As someone who's deaf (not Deaf) thank you for making it. Sadly, the vibration the iPhone makes isn't strong enough for me but this is an awesome idea and I hope you succeed with it!
John Muir, the American environmentalist of the 1800-1900's, built an "alarm clock" in 1862 that would dump the occupant off the bed at the defined time.
That would be useful to the use of the phone in general, not just to wake up. Actually, it would be useful for me - and I am not deaf. I keep my phone on vibrate all the time and when on the streets I can only feel the vibration about 20% of the times someone calls me. And I usually i HEAR the vibration, not actually feel it.
Becoming a hardware company is a little to far from you? :)