One of the most enjoyable cat toys I have ever used is an ordinary laser pointer. You can sit and move the dot around on the floor, walls, furniture, whatever. Cats love it! Of course, you must avoid shining it directly in their eyes. This isn't a problem really because they are looking at the dot, not you, and you are trying to keep it away from them anyway. I like to make the dot act "alive." It will run behind the couch or under the bed. The cat will wait to ambush it, or will look around for it. Give it a try. If you don't have one, you can pick one up for around 12 bucks.

Similar toys already exist (<a href=http://www.amazon.com/Remote-Control-Micro/dp/B0002DJ5YM"> an example); the problem is that they make a loud whirring sound that tends to be frightening to cats. A silent version would be great.

Third time's a charm...

That's really cute. I had a mini RC car and I can tell that they obviously just put a mouse body on one of those mini car chassis. They used the antenna for a tail. I suspect that if the cat knocks it over, it will not self-right itself. That could be a major drawback.