The Rectoencephalitis killer

It is now proven that 80% of hangovers come from the last beer consumed. Here at last is the device that can solve this nagging problem. First of all, buy it. Then take it with you if you go to a fair and throw the pendulum. That’s all there is to it.
The phone will ring sooner or later and if you pick it up, a voice will gently tell you it’s time to go home (and remind you more and more frequently if you don’t). No one can ever know when it will ring, but it will stop you from drinking another beer, just the one that would have given you a headache.

Video of its construction