I have a 2005 Lexus SC430, and it works in my car, albeit with a couple of caveats. You can't load your phone book into the car, and there is sometimes a loud feedback noise that lasts for a couple of seconds at the beginning of an outgoing call before the connection is made. It will probably work with the RX. I'd buy it and give it a shot if you don't care about the phone book thing. As you said, you can always return it if it doesn't work