It can't be as seamless and effortless as my imagination makes it out to be, but I think this is an awesome idea. And since libraries are all about providing contextually-relevant information, this seems like a very useful idea.
My guess is that it's not accurate enough to use in the stacks, but wouldn't it be neat that if someone walks into the local history room they'd get a message about online resources?
But even better would be to use it outside the library. Leave notes with historical information around town and create a self-guided tour; if the library has off-site events (which we sometimes do), leave notes in those places for the upcoming events; leave notes in parks and train stations about downloading ebooks or digital magazines. Like an automatic QR code people don't need to scan, or a virtual sign someone might actually read.
Of course, there's got to be some catch, because it seems this will immediately become a new form of spam advertising, with every step or highway exit being inundated with who knows what (if you can broadcast to all users, rather than picking a specific person). So it'd be neat if this functionality could be integrated into an existing library app, to provide some control over what patrons are sent. Still though, I thought this was a neat idea.