Yeah I wired it in to the wires that lead to the cigar lighter, underneath it.
The black one is earth the red and yellow one (on the V6 anyway) is power.
You can either cut the cigar lighter plug thing off the power cable then strip the outside to access the two wires inside (red (power) and black (earth)) or take it apart and unsolder the wires.
Only problem I had was I used little clip things that clip over the wires cutting through the outer sheath, dont know what theyre called, and the wires of the power cable were too thin to make contact doh