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!