lethargometer

Pronounced leth-arg-AH-meh-ter, the lethargometer is an imaginary device that judges how sleepy you are, how much sleep you really needd, lets other people know how long you'll be sleeping while the phone is ringing, and silences the ringer if the person on the other line is too persistent.

I'm really sleepy. I don't want anyone calling me at 3 AM, so I'll turn my lethargometer on!