GPS is utterly useless for finding your wife or kids (or even locating yourself) at the mall. What we need is an indoor equivalent of GPS. And researchers have been working on it.

Most recently a team of Stanford students launched a project called WiFiSLAM. Their goal is to develop mobile applications that let your smart phone pinpoint its location in real-time to within 2.5 meters. It would do it by sensing ambient WiFi signals already present in buildings. The phone's internal compass and accelerometer also come into play to help determine its location.

The students also want to create apps that could be use for marketing, depending upon what store a smart phone user is standing near. Another app might connect the user's location to social networks.

Other indoor positioning systems try to find a user's position using radio, ultrasound or infrared signals. But these approaches require special radio-frequency tags. WiFiSLAM's approach is promising because it uses existing wireless networks and the smart phone already in your pocket.

—Larry Greenemeier

[The above text is a transcript of this podcast.]