Originally Posted by BiffTheAncient
a clothes pin
a piece of cardboard
wrap 2 pieces of wire around a clothes pin so that they make contact when the pin is closed. complete the circuit by wirin in the bulb and battery. Cut a 1 inch square out of the piece of cardboard. Tie the string to the corner of the cardboard square...... blah blah blah.....
we can all see where this is goin......
You need something that simple, it'd work great, you just need to add in a buzzer or something more obvious than a little lightbulb. But yes, it can be that simple.