What doesn’t work is easiest to say. Apps that try to re-create the functionality of an iPhone app simply don’t work. If you can perform a particular operation on an iPhone, then it is better to do it there. The promise of never having to take your iPhone out of your pocket just isn’t quite here yet. The Apple Watch may advance (in hardware and software) to a point where this is no longer true but the platform has a ways to grow first.
There seems to be only three kinds of apps that make sense given the current hardware and software on the Apple Watch.
Bingo. As I tweeted yesterday, my favorite Watch apps aren’t trying to mimic iPhone apps at all. If the same task can be completed on the iPhone, I don’t see why I would try on a smaller, slower device.
The best Watch apps will be the ones that wouldn’t be possible or make sense on an iPhone.