I really liked the demo controlling the music player; it struck me as the one I'd be most likely to actually see in the near future (The door with the different

I really liked the demo controlling the music player; it struck me as the one I'd be most likely to actually see in the near future (The door with the different signs was neat, but requires a bit more hardware). I'm curious where the sensors were placed for that one (I couldn't see them on the guy's arms) and if say, getting caught in the rain or a really dry day, would throw it on the fritz.