Thursday promises to be an eventful day for the iPhone. That’s when Apple’s summons the tech press to its Cupertino headquarters to hear about the company’s plans for the mobile device - particularly when it comes to applications built by third parties.

All signs point to Apple taking the wraps off a Software Development Kit (SDK) it had promised to deliver in February. And when Apple does grant developers access to building native applications for the iPhone, it will mark a significant new direction for the device since Apple first previewed the iPhone at the January 2007 Macworld Expo.

Back in the days before the iPhone’s launch, Apple resisted calls to open the iPhone to third-party development, citing its desire to preserve the device’s security and stability. By last summer’s Worldwide Developer Conference, Apple offered developers an alternative - they could create web-based applications that iPhone users would access through the device’s built-in Safari browser.

While some software developers took Apple up on its web-based offer, others built native iPhone apps anyway. The catch was that, to install these third-party apps, users had to “jailbreak” their iPhones - which works by intercepting the communication that is supposed to happen between the iPhone and iTunes - voiding their warranty and running the risk that future iPhone software updates would render their phone inoperable.

In October, Apple signaled an end to this cat-and-mouse game, promising to deliver an iPhone SDK in February. That SDK is likely to be a major focus on the conversation when Apple kicks things off at Thursday’s event.

But the specifics of what Apple plans to say Thursday remain up in the air: How open will the iPhone be to third-party development? Will Apple place tight restrictions on third-party apps, as some reports have speculated, or will those restrictions only apply to paid apps, as others have claimed? And when third-party applications do appear - assuming some won’t be unveiled on Thursday to kick-start development—what can we expect to see?

We won’t know the answers to those first couple questions until Thursday, and it’ll take a little while longer to see what kind of native apps emerge in the wake of Apple’s likely SDK unveiling. But we don’t have to wait to offer up our own wish-list of iPhone apps we want to see appear in native form.

We convened a panel of iPhone users - editorial director Jason Snell, senior news editor Jonathan Seff, associate editor Dan Moren, and senior editors Rob Griffiths, Dan Frakes, and Christopher Breen - and told them to come up with a list of the applications they want third-party developers to burn the midnight oil creating. They came up with 25 programs they want right now, which we’ve ranked in ascending order of urgency.

25. Amazon Kindle client/e-book reader
Amazon’s Kindle e-book reader is half brilliant and half failure. The brilliant part is Amazon’s Internet system, which allows you to easily search for and buy electronic books or periodicals and download them directly to the company’s reader hardware. The failure part is the reader hardware itself, so poorly designed that it practically cries out for Apple to redesign it. Since Apple’s not in the business of doing Amazon’s work for it, how about this instead: Amazon takes the part of Kindle that’s brilliant - its Internet and payment services - and sticks them on a piece of hardware with a design that’s approximately 1 billion percent better than what Amazon’s selling. Will people really buy and read books, magazines, and newspapers on their iPhones? If you’re Amazon, it’s worth a try.

24. Photo Booth
OK, so this is an Apple application. But we’ve found that if there’s one app on our Macs that people can’t resist playing with - particularly if they’re of the kid persuasion—it’s Photo Booth, OS X’s built-in snapshot software. Adding a similar program to the iPhone that lets you apply funny filters and effects to photos you take with the iPhone’s camera would probably be a big hit, especially with the younger set. And if Apple doesn’t step up to the plate, what’s to stop a third-party developer from responding to the void?

23. Screenshot utility
Perhaps this one is largely of interest to those of us who spend our time writing about the iPhone, but we’ve noticed that writing reads even better when it’s accompanied by images of what’s on the iPhone’s screen. A screenshot application would allow us to reproduce such iPhone screens without the muss and fuss of jailbreaking a phone to install a similar Apple-unauthorised tool. And while the benefit to folks in our line of work is clear, we’re sure that people who might want to include iPhone screen grabs in everything from presentations to QuickTime movies would welcome such a tool as well.

22. Digital level
Remember that bubble level in the garage, hanging there mocking you while you’re upstairs, 60 feet away, trying to make sure your latest Picasso acquisition is hanging straight and level on the wall? Thanks to the accelerometers in the iPhone, you’ve actually got a pretty good replacement sitting right in your pocket. An application just needs to read and display the values from the accelerometers, and you could then easily see exactly when anything you’re trying to hang is level. Sure, it won’t replace a professional-grade, 4-foot aluminum level, but for odd jobs around the house, which are you more likely to be carrying when you need it?

21. Airfoil for iPhone
Rogue Amoeba’s Airfoil 3 is a terrific tool for streaming any audio that runs through your Mac to an AirPort Express Base Station or Apple TV and its attached audio system. Wouldn’t it be lovely to have a similar capability available on your iPhone? We’ll answer that question for you—yes, it would.

20. Unit converter
If you find yourself routinely having to convert yards to meters, ounces to teaspoons, and Fahrenheit to Celsius when you’re on your Mac, Dashboard’s Unit Converter widget can handle all the work for you. A similar converter on your iPhone would let you handle the same tasks on your next trip abroad while also figuring out just how low the dollar has sunk in the eyes of the international banking community.

19. Blogging client
If you’ve ever wanted to write up a blog post without having to contend with clunky Web interfaces that aren’t designed for the iPhone, then you may be in need of an iPhone-native blog client. Though the iPhone’s onscreen keyboard probably wouldn’t be ideal for cranking out thousand-word missives, a native client would likely make frequent bloggers very happy indeed.

18. Finger-paint tool
At first glance, a finger-painting app might seem like just another program to keep the kiddies busy on long plane trips and car rides, but it could also come in useful for adults too. Imagine you need to draw a quick diagram for someone, but you don’t have a pen and paper handy - just pull out your iPhone and scribble away on the screen. Your idea would take shape in no time.

17. Radio client
Sure, you’ve packed your iPhone with great music, but what good does that do you when you want to tune into the ball game or latest Presidential debate? With a built-in Internet radio client, you’ve got the best of both the pre-recorded and live-audio worlds.

16. A better calculator
TLA Systems’ PCalc is a snazzy calculator that blows the iPhone calculator away. Heck, even OS X’s Calculator can do advanced operations. How about a new calculator for geeks who aren’t satisfied with the mind-numbingly simple calculator in the iPhone? Sometimes when you’re on the go, you’ve just gotta do math.

15. Dictionary/thesaurus
Of course, a dictionary and a thesaurus are among the best weapons in a writer’s arsenal, but anybody could benefit from having that kind of information at their fingertips: crossword enthusiasts, Scrabble players, nit-pickers who like to argue about word definitions. There’s plenty of space on the iPhone for an extensive dictionary, and it would certainly be faster than having to fool around with the Web.

14. Video player
The iPhone can play MPEG-4/H.264 videos, but what about DivX, MPEG-1, or other file types? Palm OS and Windows Mobile smart phones are much more flexible in their ability to play numerous video files—a VLC-type player would be a great addition to the iPhone, and do away with lengthy transcoding in many instances.

13. Twitter client
Social networking service Twitter and the iPhone go together like peanut butter and jelly. While there are a number of good web-based Twitter apps, having a native iPhone client would likely be speedier and easier to use - not to mention immensely popular among Twitteroholics. If nothing else, it would certainly edge out the unwieldy and potentially costly option of Twittering via SMS.

12. Simple photo editor
It’s great that you can upload iPhone photos to a .Mac web gallery, but wouldn’t it be greater if you could tweak those pictures before you send them packing? With a simple photo editor that offered colour balancing, bare-bones levels control, cropping, straightening, and the ability to convert images to black and white, you could.

11. Flickr uploader
The iPhone’s camera is better than many of those you’ll find on other cell phones, but the primary ways you share photos taken with that camera are e-mail and .Mac; it would be nice if there were more options. A native program that would allow you to take pictures shot by the built-in camera—as well as ones synced from your iPhoto library—and upload them to photo-sharing service Flickr seems like a natural fit for the iPhone.

10. PDF/Comic Book Viewer
Someone give us a dedicated reader for rich-media documents. The PDF viewer inside Mail is okay, but what about a program with support for PDF bookmarks as well as some innovative navigation tools to make it easier to read PDFs on the iPhone? And while you’re at it, do iPhone-toting comic book geeks a big favour and add support for reading comic books in PDF, CBR, and CBZ formats, so we can stay abreast of Spidey’s adventures on the go.

9. Dedicated RSS reader
For those that live or die by their RSS feeds, even the best Web-based client can never take the place of a good native program. When you’re mobile, that goes double. A native RSS client would ideally let you easily download your feeds and then peruse them even when you don’t have network access, but in order to compete with existing Web-based readers, it’ll likely need to take advantage of some sort of syncing.

8. VoIP
A Voice over IP client (à la Skype) has been among the top requests for iPhone apps since the device’s introduction, so we’ve no doubt that such an application would be wildly popular. Whether or not O2 would be ecstatic about such a development is another question entirely, but from the customer perspective, it would be a great option, especially if you happen to live smack dab in the middle of a cell phone dead spot.

7. VNC client
Virtual Network Computing (or VNC) lets you control other computers remotely - think Apple’s Remote Desktop software and Leopard’s Screen Sharing feature. Since the iPhone is a portable computer, it would be great if you could use it to, say, control your home server while on the road.

6. Voice notes
The iPhone can do nearly everything you can think of, except record your voice. This seems a glaring oversight, given that the device has a microphone, a fair amount of storage space, and is powered by OS X. Adding voice note capabilities shouldn’t be that hard. Nonetheless, the lack of an Apple-provided solution opens the door for other developers to step in. The ideal application will automatically time- and date-stamp each voice note recording, and offer a method of synching them back to your Mac. Going a step further, the voice-note application could use the Maps’ new position estimation feature to also stamp a location on your voice note recording - so later on, you can not only listen to what you said, but know where your were when you said it.

5. SlingPlayer
The Slingbox lets you watch your TV from anywhere in the world, so long as there’s an Internet connection. Sling Media offers players for Macs, PCs, and phones using Windows Mobile and Palm. So why not iPhone? Granted, the iPhone’s EDGE data connection may not provide a very good TV-viewing experience… but Wi-Fi sure does. The notion of pulling out an iPhone to watch a baseball game while sitting in the airport or a Starbucks (or anywhere really) certainly has its appeal.

4. Text macro tool
As good as the iPhone’s keyboard and word recognition are you still wouldn’t want to use it to write the Great American Novel. That’s where a text macro tool - much like TypeIt4Me or TextExpander on the Mac—comes into play. Define your often-used words and phrases as shortcuts, then just type those shortcuts wherever you need them. No more pecking out “I’m sorry, but I’m not interested in your offer of an extremely low-cost bridge in the Brooklyn area” as a reply to every spam e-mail you receive; instead, just tap out !nospam, and your text macro tool does the rest of the work (and for the record, you shouldn't be responding to spam anyway).

3. Mac controller
If you’ve ever used Salling Clicker, then you’ll understand this app. Running on your iPhone, it lets you remotely control your Mac - change iTunes playback, run your Keynote or PowerPoint presentation, control Front Row, even perhaps display and interact with your Mac’s user interface. With Wi-Fi and Bluetooth support, you’ll even be able to control your Mac from long distances - perfect for those times you left that key file at home and need to e-mail it to yourself in your hotel.

2. Document editor
Sure, you can view files e-mailed to you using the iPhone’s built-in Mail program. But what about editing those documents - or maybe even creating ones of your own? The iPhone needs a built-in document editor, one that lets you create documents as well as modify those sent to you by others. This is a feature best addressed by Apple (a mobile version of TextEdit, anyone?), but in the absence of that, a mobile text editor or word processor would be heavenly. Especially if Apple ever lets us use its snazzy Bluetooth keyboard with the iPhone.

1. AIM client
E-mail and SMS are great for keeping in touch, but they are no match for the speed and dynamic nature of instant messaging. It seems unlikely that Apple will bring iChat over to the iPhone - the network providers make a lot of money off SMS, so that would be shooting Apple’s partner in the foot. But someone else should create an AIM or multi-service client such as Adium for the iPhone.

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