I stumbled across this http://omnicorpdetroit.com/blog/2011/05/04/great-global-hackerspace-challenge/
which is a barebones LaserTag system from a Detroit hackerspace which may make a good jumping off point to get a minimal working system. I didn't notice it in any of the messages or on the wiki so thought I would add it to both. Also the wiki page still has a lot of discussion on it would it be okay to remove this? and archiving it into a post to this group.
I remember talking about this with people at the pacman thing in Milton Keynes really pleased that things are starting to develop.