FM Transmitter Case is an app that allows you to play music from your iPhone or iPad over any FM frequency, for use in your car or home. You can access your full music library on your mobile device, sending it through an FM transmitter to any FM radio.
The FM Transmitter Case interface is clean. It shows a rotary dial with FM frequencies displayed on it, as well as a digital readout in the center. There's a set of buttons at the bottom for favorite FM frequency presets, as well as control for your music streaming. However, to use FM Transmitter Case you need to purchase the FM transmitter that goes with it, and that can be hard to find (it isn't available for purchase through iTunes). We did try several FM transmitters, and they all worked, but the setup is bulky and not very friendly.
If an FM transmitter is your only option for getting music from your iPhone to your car or other device, then FM Transmitter Case will work for you. But the cost is considerably more than alternatives such as a straight cable, cassette interface, or CDs. FM Transmitter Case worked for us, but we don't think we'll ever use it again.