Yea, GPS seems like a solid solution - but weight, battery life, and reliability seem like an issue to me.
Lets be honest, a quad is unlikely to be more than a mile from your location in just about every circumstance. A 'simple' lightweight, self contained beacon that pings for a month seems like the 'best' solution to me. The model rocket guys have been doing it for a bunch of years - either with home made units or all-in-one systems like this.
Might not be as quickly 'spot on' as GPS, but following a ping isn't exactly rocket science. Once you have the relatively expensive receiver, you can just stick a new transmitter on each of your models.
