A worldwide roaming agreement between four of the world's biggest wireless operators has given the WiFi hotspot market a shot in the arm.

UK-based BT; StarHub of Singapore; T-Mobile International, which operates in Austria, the Czech Republic, Germany, the Netherlands, the UK and the US; Australia's Telstra; and Telecom Italia, under the auspices of the Wireless Broadband Alliance (WBA), all agreed to share hotspots - meaning that any of their customers should have instant access to over 20,000 hotspots in 11 countries across the globe.

Each company has announced the agreement individually, and although all have agreed not to charge other people's customers for access for the rest of this year, charges - as yet unannounced - will be introduced in 2005. As such, while all benefit from the others' infrastructure, the company with most hotspots - in this case T-Mobile - remains in the strongest position.

BT and its Openzone service is not far behind, having already agreed a roaming agreement with T-Mobile earlier this month, as well as others with The Cloud (UK), Telia Homerun (Sweden), Sonera Homerun (Finland) and Airpath (US).

All WBA members should in theory be able to log-in at any international WBA location as if logging on to the company's own hotspot, simply by selecting their operator from a drop-down list and sticking in their name and password.

BT Openzone currently charges £6 for an hour and £10 for 24 hours. T-Mobile U.K. charges £1.50 for 15 minutes, or £5 an hour, with tariffs ranging up to 720 hours for business users, while prices in the rest of Europe are similar, depending both on which country you're in and the exchange rate.

"This announcement redefines the way that international travelers will stay connected while travelling internationally," said Kyong Yu, chairman of the WBA.

"For the first time ever, the customers of our participating carriers will be able to roam across broader international wireless broadband networks with one account. These roaming arrangements set the standard for a uniform and consistent approach to international roaming that should help drive widespread adoption of wireless broadband."