Plazes released a Mobile Plazer. They are using cell-tower geolocation, similar to GSMLoc. It will be interesting to see how they handle many locations belonging to a single Celltower location, as well as cell-towers being carrier specific.

They address the issue in their FAQ:

After setting a Plaze the first time (e.g. by entering an address), it was necessary to enter an address again the next time I started the application at the same location. Why?

A newly discovered Plaze is bound to the GSM cell tower your mobile was connected to. The areas of cell towers overlap, so sometimes your mobile is connected to a different tower at the same location. Simply enter an address an set the Plaze a second time, then Plazes knows both cell towers and it will work better next time.

This is really cool. Geolocation by mobile without a GPS system is key to Location-Based technologies to take off and be generally accepted. Plazes is leading the edge of the community-based geolocated networks. Now time to build some services on top of their framework.

- via Henri Bergius