I installed a
[$40] in the JK this week. I also needed a Kensington Noise Reducing AUX Audio Cable [$15] and a 3.5mm female to female connector [$2]
Not a very exciting mod but enables me to listen to music from my phone, make and receive phones calls and listen to directions [just to name a few advantages]
Very easy to install - just plugs into a power socket and the 3.5mm aux input on the stereo. It has a disc like button about the size of a 50c coin that has a built in mic [stuck to dash]. I can answer calls with this, skip songs and it even accepts voice commands with my phone.
Because I installed in into the cig lighter - it turns off every time the car is turned off - meaning it doesn't drain my battery - and automatically reconnected when I start the car up again.
I am very happy with the result. I can post pics if anyone wants more info. Heaps cheaper than a new stereo or a mygig mod - im in a 07 JKU