using a miniature Model #3 808 keychain spycam with 8GB microSD card
triggered by a PIR motion detector
and steered by Arduino chip.
After issuing signals to camera buttons, Arduino chip is put into power-down mode waiting for the next interrupt to come from the PIR detector. Power consumption in power down-mode is 0.4 mA from a single LiPo cell.
Please see detailed description in the pdf file.
Example video from snapshots: