Here’s a way to make sure you don’t leave your Leatherman multitool somewhere. It’s an alarm system that will start a timer when the tool is removed from the holster. After five minutes the module beeps to remind you to put the tool back where it belongs. Annoying? Possibly, but if you’re not done with your work just press the
reed leaf switch on the module to reset the timer. A PIC 12F683 handles the timing and generates the waveform for the piezo buzzer. Perhaps this could have been accomplished with a dual 555 chip like the LM556 (one timer for the countdown and another for the piezo waveform) but the PIC has power-down modes available that should make the button batteries last a long time.