The BBC has launched a free iPlayer app for the iPhone and iPod touch that supports video streaming over 3G.

Until now, smartphone users iPhone users were limited with the BBC mobile iPlayer site for watching live and catching up with old TV when away from home.

The new iPlayer app offers essentially the same service, but also supports video and radio streaming over the 3G data network — the iPlayer web site only supports Wi-Fi.

The app will automatically detect the quality of a 3G connection and adjust picture/sound quality to suit, so programmes should be accessible even in areas where network coverage isn’t so great.

Remember that streaming video over 3G is a sure-fire way to wipe out a 3G data allowance and rack up excess data use charges though, so it’s something that’s best used sparingly.

The iPhone/iPod touch app is available now from the iTunes App Store. The BBC is also working on a new 3G-enabled version of its iPlayer app for Android and plans on releasing an update early next year.

[iPlayer for iPhone]