Get an
InvisibleSHIELD. I have one and it works great! The install is kind of a pain, but just make sure you wash/dry your hands well before you install it, use plenty of solution, and make sure that you install it in a lint-free environment (or as close to one that you can get). Also,
take your time with the install.
Second, the
Monster iCarPlay works well as a transmitter. It's the best FM transmitter I've used so far. I live near several large cities, and it rarely craps out on me. However, just so you know, since it's "not compatible" (not specifically made for the iPhone), you will need to put your phone in airplane mode to get it to work like an iPod. Otherwise, there's the annoying "GSM Sound". Also, if you need to change the station, it's really difficult on the iPhone because iPhone refuses to use the Monster OSD. It becomes a guessing game.
Hope this helps. Good luck!