Turning Frog (Sound Sensor)
This robotics initiation kit includes 2 motors with gears to be assembled and a microphone to be used as a sound sensor. This is an interesting robotics kit. It requires 2 x 1.5V type AA batteries and a 9V battery all sold separately. 
Caution: soldering iron required.
The Robot is able to produce sequentially repeated movements when it detects a sound: the frog starts up, moves forward, stops, turns left, stops, turns right and stops. 

Turning Frog (Sound Sensor)