MagicMap is a free framework for indoor positioning based on Wifi and Bluetooth signals.
A list of other partly commercial services: Indoor RTLS systems
WiFi & Bluetooth based
Ultrasound + RF based
RFID (active) based
Blog entry on passive solutions. The industry term for this is RTLS (Real time location system): Passive RFID providing RTLS Real-or-hype
A startup offers feeds for thousands of sensor devices—and wants others to open up their data, too.
Distributed wireless sensors are increasingly being used to monitor all sorts of things—from water quality in a river to the oven in your kitchen. A startup in the U.K. called Pachube wants to kick-start a revolution in new apps and services by providing ways for anyone to share and access all this sensor data.