I'm covering the "peer-to-peer" location technology from Navizon in my next Rafe's Radar column. Peer-to-peer is in quotes here since Navizon's system relies on users to record the locations of WiFi access points and cellular towers, but isn't strictly P2P, as it has been pitched. It's still very interesting.
I'm also curious about a company called GeoVector, that goes to the next step and apparently can determine not just where your handheld device is, but what it is pointing at. My attempts to contact the company have not been successful (this almost never happens). If anybody reading this knows people at GeoVector, feel free to point them in my direction: firstname.lastname@example.org.