Bell Atlantic already announced a joint venture with one of the electronic navigation companies to supply drivers with position info using cellular triangulation.
Not to mention our very own Omnitracs service, which uses spread spectrum ranging via satellite to report the position of every mobile user to roughly GPS accuracy (without actually using GPS). So far the trucking companies to whom we sell this stuff have been pretty enlightened in how they use this information. We've also discussed adding position location to our CDMA cellular system, although that wasn't originally a design consideration. Depending on how far you go with modifying the existing system, and depending on local terrain, you could locate a user somewhere on a circle around a given cell (by round trip time measurements from cell to mobile and back) or perhaps to a specific point by multi-cell delay measurements during a handoff. Which suggests a "stealth" phone that randomly dithers its round trip delay a la GPS selective availability... Phil