also, based on some quick research on Ramsey Electronics' website, the below would have a big restriction on FM transmitters. While this is talking about an FM broadcasting kit, the #2 means that if you do get static on your frequency, there's not a thing you can do about it. Not something you want to tell a consumer when you can give them access to a $5 cord and have perfect signal.
The individual kit-builder and all users of this device assume responsibility for lawful uses
conforming to FCC Part 15 Rules. Operation is subject to the following two conditions:
1. This device may not cause harmful interference, and
2. This device must accept any interference received, including interference that may cause undesired operation.