OK - it's total vapourware at the moment but there's a RFT for a project that allows a wireless PDA (probably 801.1b) to act as an information guide for an art gallery - listing additional information about particular paintings etc.
However, ideally the content should change as the user walks around such that they are presented with info pertinent to the section they are in (granularity ~1m).
Is this feasible - I can't think of how the PDA would know where it is - GPRS is out, as that would add too much hardware cost.

Any ideas?