Movement sensor to trigger an electric motor - supercheap!

Hello Any electronics whizzes out there? I want to develop a kids toy that reacts when a child moves within a certain range of it. (Remember that game "Grandmothers Footsteps" where you have to creep up on somone but become motionless when they turn around - if you're caught moving you're out.) The sensor and the circuitry (and some moving parts) need to be able to fit inside something the size of a pint glass, run off batteries and preferrably be drawing no current when no-one is in range. Please - if you have some ideas on this drop me a line and I'll explain further. thanks for looking this far! Julius (London, UK)

Patented8 years ago
Hey that make me think of this billy fish that start to sing and to move( with a motor) when you past beside, its exactly what you need ( movement trigger motor), you can take the same component and the basic of the circuit to build your toy . It run on 2 AA battery and I don't think it drain battery and all the components can easily fit inside a pint glass, look at this picture.(try this in google for more picture: billy singing fish or boogie bass )

Ive just found the perfect things, this is a website that show how this fish work , I think you will have everythings you need there(it explain the circuit)
here is the links:
julius100 (author)  Patented8 years ago
nice idea. I used to have one of these but the fish's skin started rotting! I found that the light-sensor was only effective in certain lighting situations. I'll see if i still have my fish in the attic. Julius
Correction : it run on 4 AA battery, and the movement sensor seem to be a photosensor