I wouldn't put that on the iPhone, though. I spilled an apple martini in my Eee and it was a huge pain in the butt. It took forever to find a source for a replacement keyboard. 😱
It actually doesn't effect battery life that much. I've been using it for a while, and haven't noticed any decrease in battery life. It's cool though, it's nice to have another form of feedback. The vibrations are short, so it's not annoying.