I know this isn't a useful comment yet, but I know I've heard of bluetooth games that can be played like that (cross-platform). I'll try to find where did I read about that...
Edit: OK, I remember at least one now: Elements interactive's "Quartz 2".
Edit2: Also, "Super Miners" by InfiniteDreams, but I know that game isn't compatible with all pocketpc bluetooth stacks (you'd have to try it on your pocket pc).
I think you should search first for multiplayer bluetooth games on the S60, and if they have a counterpart here as a pocket pc game, then it's possible that they work together.