iPod touch 4 running Apple TV Lowtide interface
Lowtide runs the Apple TV interface, similar to how SpringBoard runs the iPhone, iPod touch, and iPad home screen system, and it looks like Apple designed the built-in iOS app with cross-device support because developer Dunstin Howett got it up and running on an iPod touch 4.
Erica Sadun from TUAW has the details:
This is probably not something you'll want to do yourself. And the reason is pretty technical, so please excuse me while I get all jargony on you. Extracting frameworks from the iPhone's "dyld" cache system was not enough to get the app to run (an approach I initially tried). Instead, you need to use caches native to Apple TV, which is the approach Howett used.
So it's more a proof-of-concept than anything practical at this point, but getting things to run where they ought not is like climbing a mountain -- because it's there.
Video after the break!