Neg on the power, just the standard omni mic.. I don't believe it effected the battery any and if it did, very minimal. The mic's are custom made and available with different lengths of cord.. I suggest going with the longest available.
I have been experimenting with mics in the Caterham as the noise factor is a major issue with track videos.
Here is a Gopro HD2 with an unpowered mic cheapie Olympus ME15
Sounds tinny and hollow. The reason for this is there is only a limited amount of power the Gopro puts down the mic wire to operate the mic. So you do miss recording the dynamic range of sound that is in a car. I have not experienced any difference in battery life with or without mic.
For contrast here is a GoPro HD2 with a powered Audio Technica mic, same car, camera, location, etc but different day and with a passenger.
Sounds better to my ears although I am getting some electrical interference around 6 minutes that I have not sorted out.
El Dude has found the first really good unpowered mic for a GoPro that I have heard with a good mounting location that avoids wind (the killer for car mics) -great find! :up: I would love to compare it to the Giant Squid powered mic option as I suspect it would be even better.
It probably comes down to how much you want to spend?