Filament alarm/sensor

This started out as a quick'n'dirty hack for my printer but I've found it really useful so far.
It's a printed base with a battery, buzzer, switch and some PTFE tubing.

Your filament will run in the short PTFE tube and along the way holding the switch open, disconnecting the buzzer circuit.
As soon as your filament runs out/passes through completely, the circuit will close and the buzzer will start singing the song of it's people.

This instantly lets you know it's time to hook up a new s