Adding costum properties to a user

Is there a way to add costum properties to a user. Actually i need to store x y cordinates to store somewhere without a using a database.

I have a version working wich is storing these cordinates in the nickname, but this technik trigers the presence twice. Ones when the old nickname is unavaible, and after when the new is set.

Does anyone have some other ideas how to do this. It would be nice to get rid off the presence technik and do this with the group message but when somebody joins a room i need to get the others XY cordinates so its needs to be stored somehow.

thanks for your help