It is possible to use all "on purpose". But for most general use, I think it's not so easy to reach that limit and it is not critical, IMO.
Took Canon a LOOOOOONNNNG while to restock on these, so I grabbed one the moment I saw it at Key Color, Mid Valley today.
The 600ex-rt are also flashes, but with built-in wireless trigger as well. The st-e3-rt is basically a 600ex-rt, without the flash part.
Doesn't do much at this point. The SDK isn't out yet so no 3rd party apps, hacks at all. But I get notifications from my phone which is a big deal for me that keeps the phone silent 24/7.
Not exactly a toy but I coded my first Pebble watchface Download: SplitText | My Pebble Faces Fun stuff!