Trying to find a buzzing vibrating device...?

This may seem a strange Q but here goes: I am trying to find a device which will vibrate and "buzz" (no not for sexual purposes) but something which I want to do some experiments in consciousness from sleep state. I need this device to attach to myself then go off at a certain time say 2 hours from when I go to sleep so I can be sure I am asleep when the device is activated. Trouble is I don't know what to use to vibrate at a certain time and its not like you can really buy anything like this. So I wanted to ask people if they knew of something that could be used for this purpose which could be made to vibrate at a certain time? thx.