you can buy one that is a security light. when it is triggered the light turns on and the camera starts to record on an SD card slotted into the side.
Click Here Pricey at 99.99 or 79.99 @ B Grade price. its reviews are not as good as hoped
But at that price you could buy a video card and record onto a Desk top pc with multiple camera's. the only good thing about it is installation (just 1 power cable)