The guys in the local Model railroad module club have a system they got about 3 years ago. It is not rechargeable but does color and sound.
I think it was under $100. They just put the unit on a flat car and push or pull it around. I was very impressed with it but have not seen any video with sound units in operation yet. I can tell you the video quality was very good, even going on a vcr tape. I spent hours watching various video to make a DVD for them, but did dub the sound for more realism.