We use vibrating alarm clocks. If you're only hard of hearing, a regular alarm clock can still work as well. My favorite alarm clock had a vibrator and sound, but it also had a socket for my lamp to plug into, so it would wake me up in all 3 ways. Fantastic for waking up at 6AM when I just wanted to either kill myself or go back to sleep. (Sadly, when I was at NTID, the socket for the vibrator to plug in broke.)
EDIT: but seriously how do deaf people wake up?