The "unforgettable" purse

The purse registers whether certain objects (e.g. keys, wallet) are inside or at a close distance. If one of the objects moves out of this area the purse warns by soft vibration at the shoulder and you can react accordingly. In case everything is alright, e.g. you gave the cellphone to a friend to let him use it, you can "tell" the purse by shaking it softly. Then it stops warning you.

http://interface.fh-potsdam.de/popups/koch.html