It's a cheap Chinese version of a dash cam. Another Â£15 got me a class 10 32GB SDHC card, so for under Â£30 I have a dash cam that can record over 5 hours of footage.
Here's a sample video from my commute tonight... http://youtu.be/xSH-kxq88SE
The camera comes on and starts recording when you plug the charger into the cigar lighter socket (or when the ignition comes on if you wire it into an ignition switched power supply), and it switches off when the power goes off. It records in AVI files of 2min/5min/15min length (you set it).
It's not fabulous HD quality, the sound is pretty poor, but for the money it's well worth it. Could be very useful in the event of an accident to show what happened!
2004 MG ZT+ CDTi 135