Bluetooth treasure hunt question: Your help needed

I got this email in from an avid SMS Text News reader today. Have a read. Any ideas? I’m scratching my head with this one.

Hi Ewan,

We’re trying to organise a team challenge for our colleagues here. We’re going to do some kind of treasure hunt with a mobile twist – GPS, MMS, barcodes etc. I was wondering if we could include bluetooth somehow. What I want to acheive is to send a clue of some sort – text, whatever – to people within proximity of a certain location, much like you got that ad from the marylebone tup the other month.

I’ve found ways to do this from dedicated devices or laptops, which is fine. But surely there’s some way, like an application, of doing this from a handset? Ideally, a cheap way? Without having to manually pair with everyone?

Hmmm.

I immediately thought of the bluetooth service providers I know of (e.g. Bluepod) — they could certainly do this but I’m willing to bet their equipment might be a bit too expensive for an office treasure hunt budget.

Any thoughts?