I use the Motorola Roadster (available for about $50 on Amazon) with my Focus. It holds a charge for a few days (comes with a car charger), and the FM transmitter works flawlessly. Much better than "wired" transmitters I've previously purchased at Best Buy. (Obviously, if you have an aux input with your car stereo, that will get you good quality).
Plus, it works as a Bluetooth speakerphone with voice dialing.
i bought a monster fm transmitter on amazon, it was around 30 bucks. but it is by far the best fm transmitter on the market. it literally gives me hd quality sound ( on my htc hd7) and i live in a moderatly populated area, so lots of radio stations. it is never fuzzy unless i am taking a long trip and then it is just a matter of changing the station. it has 3 preset stations which are programmable. no batteries required of course. and yes fm transmitters will work for any device with a aux out. has nothing to do with the OS.