Kent-based mobile VoIP provider Truphone hopes to make its software compatible with 25 mobile handsets this year.
James Tagg, CEO of the company which routes calls from regular mobiles over WiFi internet, told GigaOm Truphone will shortly work on Symbian S60 and UIQ (largely Nokia and Sony Ericsson) as well as Windows Mobile.
Meanwhile, Truphone also said its products link up with Google Talk, allowing mobile users to speak with online contacts using the search giant's IM and VoIP standard.
The company also "plans to soon offer services such as SMS-over-IP, video over IP and location-based applications", in what may be a sign of a growing erosion of mobile networks' traditional revenue sources.
Working out of a converted barn, Truphone recently scored £12.5m in first-round funding.