I once thought of an evaluation of the board. You prposed a material count, but an evaluation by Rival (Russ' and Chris' chess engine) would be very cool. But I think this is not possible, because it takes too server time to calculate this.
so we will see what the future brings... (Russ, could it be possible to export (per xml or so) the fen string and that I let think Rival automaticaly (??) on my webserver??)