Security Systems...... I need Help...

Hello......
I have to do an electronics project for a technical exhibition in my college. The theme is Security Systems. Anything related to this topic will do. So can anyone suggest a good project which i could possibly do...???
Please Help Me.......!!!!!!

for home security systems, a combination use of motion detector , IR sensor, door/window sensor , sound detectors will help u ..

Well...... Thanks for your suggestion....