My girlfriend is partially deaf in one ear, so sometimes she will oversleep if she is lying on her good ear. A while back I built her an Arduino-powered alarm clock that uses a servo to repeatedly poke her with a foam finger (those big hands you wear at football games). It was a shoddy prototype, but the cool part was it synchronized with her iCal calendar.
So, to answer your question, some [partially] deaf people use a makeshift Arduino robot that is duct taped to the wall next to their bed.
Oh my goodness, that's brilliant. My boyfriend is partially deaf and also the heaviest sleeper I've ever met, and oversleeps pretty regularly even with the loudest blaring alarm I've ever heard, a wake-up light, and a vibrating alarm under his pillow. As a relatively light sleeper with normal hearing this combination nearly gives me a heart attack every morning, while he barely rolls over until I hit him enough times to actually wake him up and turn his alarm clock off, but if I'm not there he tends to oversleep a lot.
To answer GP's question, some partially deaf people use grumpy significant others as an alarm clock. But I might have to look into a similar robotic setup.
So, to answer your question, some [partially] deaf people use a makeshift Arduino robot that is duct taped to the wall next to their bed.