The iPad app store has accepted the first VoIP application, Truphone. The Truphone app on the iPhone allows you to make VoIP calls over wireless networks. The iPad version has similar functionality although due to the larger screen the iPad offers, the new iPad version of Truphone shows more details on screen relating to your call.
It has not yet been verified but it is common assumption that you will probably be able to use Truphone to make calls over 3G networks. We believe that you will be able to unless the 3G network provider (AT&T) puts restrictions on the app. The press release does indicate that this will be possible although it's still not crystal clear just yet:
'Analysts estimate that Apple pre-sold more than 150,000 iPads on its first day, with 2010 sales on track to hit 4 million, said Geraldine Wilson, CEO of Truphone. 'Every device includes Wi-Fi, and soon,
3G connectivity. That makes them a natural fit for Truphone
, which has a long history of giving the iPod Touch and iPhone a broad range of new options for staying in touch. We're excited by the opportunity to extend our suite of convenient, dependable, high-quality voice functionality and IM services to iPad owners.
Also when looking over the Truphone app in the app store, it only mentions WiFi, probably because the 3G iPad won't be on sale till the end of the month.
We expect that the other VoIP apps such as Skype will follow suite and build their VoIP apps to more suit the larger screen.