Hugely overpriced and better solutions available,
This review is from: R.O.GNT Transmitter - Black (Accessory)
Customer review from the Amazon Vine Programme (What's this?)
This isn't an iphone case, it's just a slightly larger bumper that incorporates an FM transmitter. The idea is you tune your car radio and listen to your iphone's audio without the need for cables.
Thing is, an FM transmitter is normally a cheap workaround. This product is £50. You will actually find, on Amazon, full car radios with Aux inputs, MP3 compatability, SD card slots and USB ports for £35! If you have this amount of money to spend, you would be far better served getting such a device and dragging your favourite MP3s onto an SD card or USB stick. That way you never have to worry about iPhone battery drain, transmission and sound quality, or the fact you keep needing to remove this bumper to access your normal connection port.
If you really want an FM transmitter, find something much cheaper. If you have more money to spend, upgrade your car's sound system. There's not a single good reason to splurge fifty quid on this.