Cell phones are now ubiquitous, and cell phone data is fast becoming a standard tool for search managers. You will recall that a few stray cell pings played a controversial role in the famous Kim search in Oregon, back in late 2006.

Depending on the the phone and carrier, a cell phone might provide GPS coordinates directly to the location of the phone. Even in "no service" areas, the odd ping might be picked up by one or more towers, and tower sector (directional) info might be obtained which can provide a rough location. Using this information tgether with topography, GIS can be used to estimate where the signal could be comming from, and which areas are almost certainly masked by terrain (ie. where the signal could not have come from).

A search manager almost never has enough resources to thoroughly search everywhere. Thus the task is to deploy resources in the most likely areas first. Any tool, such as cell phones, that helps narrow down the search area is hugely beneficial to the search manager. Because of legal and privacy concerns, it is usually necessary to have law enforcement involved in order to get this data from cell service providers. The actual technical work may be done by specialty teams, such as from CAP.