you can check out wifiscanner.
It looks as if the signal strenght of the node you are trying to find will change as it gets stronger or weaker. Not exactly sure though.
Linux OS. You could try this with a VM session for XP not sure how well it woks that way.
Let us know if you get this working, seems like a good idea to be able to find a user on a wireless network for security reasons, e.g. someone wants to deauth or start running arp poisen attacks.