How about intelligent directions to stop passengers getting lost?
Display screens that can show passenger name and directions when the passenger is within a set distance of the screen. Since there is a limit to the number of prople who can stand within range of one screen, it should be able to handle the capacity.
How about more targeted announcements:
"Would Passenger Smith traveling to Nowhere please go to gate 987 immediately" can be broadcast only to the speakers within range of Mrs Smith.
And take this out of the airport - cheap, accurate tracking of anything in a large space.
Patients (and maybe even Doctors) in hospitals.
Kids at the supermarket/shopping mall.
Yeah, OK, I concede - it's going to be used for advertising :(