They did have one but i guess it got cut due to budget restraints (someone correct me if they knwo the real reason). You can however get one through Cydia that works on Wifi or 3G if you have unrestrictor.
The BBC iPlayer site works perfectly on the iPhone (and has a very nice iPhone specific layout) and you can watch programs. Do they really need an app?
They are working on one. It has been delayed because greedy newspapers nagged the BBC trust to investigate the development of apps and if that fell within the BBC's remit.
A few weeks ago the BBC announced they had been given the green light, and they released the news app while saying the iPlayer app will follow.
The BBC iPlayer site works perfectly on the iPhone (and has a very nice iPhone specific layout) and you can watch programs. Do they really need an app?