Mood Ring Party Finder

Mood rings are pleasant, vague, analog devices. What fun might come of programming them?

How about a "find the party" service? Your host publicizes the date and time of the party, but not its location. Your task is to find the party using only a mood ring, which changes color to indicate how close you are. There's no directional advice, just "colder/warmer".

This might actually be quite cheap and easy using newer cell phones, which have (a) GPS receivers; (b) Bluetooth transmitters; and (c) the ability to run non-built-in applications. The distance-finding logic would reside in an app that runs on the phone and connects to a server to learn the event coordinates (kept secret from the user). The app would compare current location with desired location, probably do some logarithmic scaling, and broadcast a closeness value over Bluetooth. Your mood ring would be a cell phone accessory that required only two parts: a Bluetooth receiver (very cheap as I understand it) and a pair of LEDs of different colors that fade and blend. If the mood rings are cheap enough, the host could mail them out prior to the party, though I admit it's problematic that some guests might not have compatible phones.

The LED fader is already available as a raver accessory, and costs something like $1. But that kind just fades in a looping pattern. What if, once you reached your destination, the event location was broadcasting a Bluetooth signal that made all the mood rings at the party oscillate together, in time to the music?

Is this actually cool, or am I just a dork?