We made a motion sensor for people who are parking. This means that if you were parking and you got close to the wall then it would activate a buzzer which would ultimately stop you from crashing.
We decided to base it around parking as we aimed to prevent people's cars from being damaged.
In our littleBits prototype we used a motion sensor, oscillator and a pulse. This made it so that when someone triggered the motion sensor it activated the oscillator which went off in a pulse fashion.