iOS developers Steven Troughton-Smith and The MudKip were able to hack a current-gen Apple TV so that it can run iOS apps at full screen. This was done by creating a custom Home Screen for the Apple TV, which was jailbroken.
So far it seems that many of the currently existing apps work well on Apple TV, which is basically an iOS device that’s powered by an A4 processor, but has none of the internal storage. This isn’t entirely surprising considering that the set-top box is basically an iPod touch that lacks a screen and the storage capacity. It’s also reported that Steve Jobs has said in the past that an App Store could come to Apple TV at some point.
It’s not available yet, and there is no ETA. Looks like we will have to wait a while.