We have a lot of customers asking how to get their iPad to play sound through their car speakers, and so I thought I would start a thread of some solutions that I found that work.
There are basically two ways to get sound to play from your iPad to your car speakers.
The first way is by FM transmitter. The FM transmitter plugs into your iPad and allows the audio from the iPad to play on a radio station that you choose on your car stereo. This solution is simple, however rarely sounds good, and you typically get a lot of feedback and are constantly changing the station to find a clear signal. I wouldn't recommend this option.
The second way is with an auxiliary input. Either you already have an Auxiliary, USB or ipod plug installed in your vehicle, or you can purchase a kit to allow one. You can simply plug your iPad into the port and be done, however you still have a cord that is dangling from your iPad that I don't like. That is where Bluetooth comes in to play...
Adding a Bluetooth system that can stream audio is the way to go if you don't want any wires seen from your iPad. You can install a Bluetooth kit AFTER YOU HAVE AN AUXILIARY SOURCE. The bluetooth signal is very good, and nothing like the quality of a FM modulator. I would completely recommend going with a Bluetooth unit.
Here are some companies that make Auxiliary input adaptors that work with your factory sound system. I would recommend getting an Auxiliary adaptor not an ipod adapter. The ipod adapter allows your factory radio to control the iPad and not you. Once you buy the Auxiliary adaptor then you can purchase the Bluetooth adaptor if you don't want any wires to be seen.
Auxiliary adaptor companies
iPod Integration for your car and More by Pac-Audio - Connecting you to the future
I have only found two kits that allow you to take the Auxiliary input and transform it to Bluetooth. The two kits are called the Scosche MotorMouth 2, and the Belkin Air Cast. Here is a run down on the units
Scosche Motormouth 2
The Scosche unit is designed to plug directly into your auxiliary input. There is a small button on the side of the unit that allows you to sync with your iPad. The Motormouth has an internal battery that will last about 5 hours before having to be plugged in. The unit does come with a charger, however does not work while being charged. This solution is nice and clean, however I think it should come with a hard wired option, and should auto sync when you get in the car.
Belkin Air Cast
The Belkin Air Cast is a great solution for the vehicle, and I personally have this installed in my car. The Belkin Air Cast is designed to plug into your cigarette lighter, your auxiliary input, and then mount the controller on the dash. I actually hard wired the unit, so all I have mounted is the controller on the dash. The install is very clean, and simple. When I get in my car I just press the controller and it automatically syncs with the iPad, and starts playing music from where it left off when I shut the truck off.
Yhis is a picture of my dash with the Belkin installed
You can purchase the Motormouth now on my site, however the Belkin won't be shipping until 4/14/2011.
Bluetooth accessories for iPad