I don't know if they're small because they're on the wrist or because they're sold as watches.

I don't think I'd be against having a bigger screen on my wrist like control panels that have been seen in SciFi shows for many years :) Something smaller than an iPhone, but maybe like the iPod Nano would work.

I wouldn't be surprised to see them appear soon. Sometimes, I feel that I could use my iPhone on my arm rather than my pocket, when walking for example. But the smart watches tend to have too little screen real estate.