Tri-Edre Software has released CheckUpdates 1.0.0, a utility which monitors your non-Apple applications to ensure they are up to date.
The software runs natively on PowerPC and Intel Macs. It builds a list of what you have in your Mac OS X Applications folder. It then regularly checks manufacturer websites for new versions of named applications.
When a new version is detected, the menu blinks and list the application(s) with a new version. Selecting an application in the menu brings you to the relevant software update page.
The software costs €10 (about £6).