Over time, we have featured a number of alarm clocks. This not being a clock based site as you may have noticed, all of these have had their own USPs. But all of them also promise to achieve the same end result - manage to wake you up.
Watch the video for more action
The Mathematical Alarm clock can be summed up by saying it wont stop ringing until you solve the mathematical equation flashing on its face and give it the answer. Since scarcely anyone I know can do this while drowsy, leave alone in sleep - I think this clock safely does as promised.