A reliable (modified) alarm clock that will wake the dead. I put this together after having several wind-up alarms break on me. It's basically an electronic alarm clock modified to trigger an alarm bell. Since I'm pretty much comatose when I sleep this is just what I needed.
Here's what you need to make this:
1.Alarm clock - mine is a cheap one that I got from Walgreens. It gets it's power from the mains and has a 9v battery for backup. I don't remeber how much it cost but it was probably less than $15.
2.Some basic knowledge of electronics and construction techniques. (really?)