My radio was first implemented on a panStamp which is ATMega328 based. I then ported the code base to a standard ATMega328 Arduino board (the Infiduino which runs at 3.3v). This opened up a world of possibilities of what could be done using this non-PC based and battery operated approach.
I had developed a Retro Transformer - a standalone box containing a panStamp radio. This little box could control the main functions of MTH engines (startup/shutdown, speed, direction, horn and bell).
Another developer, Ray, used this same approach but he built up a Retro Transformer using an Infiduino and an Elechouse CC1101 radio. He sent me a video which I put on my web page: