Among the announcements made by Apple at its January 27 media event, a change in the SDK of the iPhone was also announced – a move that will allow the iPhone users to avail voice-over-IP (VoIP) calls’ facility over 3G data networks. Thus far, the VoIP service on the iPhone was available only over Wi-Fi connections.

With Apple having confirmed the SDK change on Thursday, a number of companies offering or VoIP said that the Apple iPhone will henceforth support their applications. The change is applicable to all applications for the 3G-enabled iPhone as well as the newly-released iPad tablet device, other than those that use AT&T’s 3G network without AT&T’s permission.

While Apple has vowed to get VoIP applications into its App Store, the iPhone users can avail the Internet calling services over cellular networks only if their carriers comply for VoIP calls to work over 3G, over and above the Wi-Fi.

Apple’s decision to allow VoIP service over 3G networks has been commended by the Federal Communications Commission, which is currently reviewing Apple’s non-approval to the Google Voice service for the iPhone as well the competition in the wireless industry.

All praise for the Apple move, the FCC chairman Julius Genachowski said on Thursday that it is “an action that will create new opportunities for entrepreneurs and provide more choices for consumers.”