SOCIAL: Sensors motion light and sound experience?

[Adrian Cotter]

Does anyone out there have any experience with diy or educational  
level sensors (light, motion, and sound in particular)?

I have an idea for an art installation (city arts comission store  
front program) but not 100% sure I can do what I would like to do.

Found some sensor technologies for school labs, and Sun has some  
system, but was wondering if there were others out there. Aiming of  
course for low cost.

Let me know if you have any thoughts and I can give you more details.