This troper once found himself and two other family members searching through the whole house looking for something beeping thrice, every thirty seconds. At first it was thought to be a fire alarm with a low battery alert - nope. Then the carbon monoxide monitors. Nope! It was finally deduced, after around fifteen minutes of searching (usually waiting for the source to beep, then moving towards it in a mad game of Marco Polo)...to be a cell phone with a half-dead battery.

This troper's father is a biological version of this. "Did you do yet? You only have until ." "Dad, you said that one minute ago. I. Know. Already."

I worked for Avis once and picked up an out of service car that the customer said had a repeated beeping noise. Brought it back, heard the beep once but couldn't find it while driving. Mechanics worked on it for two days, couldn't find it. I needed a car to pick someone up, and that was the least beaten up of the OOS ones available, so I nabbed it, and the beep went off while I was waiting for the gate to open. Dove under the seat, and found the problem; a pager complaining of a low battery that had gotten lost under the seat and somehow bounced up into the springs where it wasn't easy to find.