Anyone for a fight?

We've talked about sumo for a while now. It's been one of our goals to get some sumo up and running.
The way we see it, we need to do it in three stages:

1. Get a Zumo chassis up to an operational stage.
2. Program a Zumo chassis to detect an edge, reverse from it, turn around and run across the sumo ring.
3. Be a bit more clever and get a Zumo to detect another robot (maybe using an ultrasonic rangefinder) and push it out of the ring.

We have started to make a sumo ring... This will be finished in a couple of days!