Sorry to rain on your parade dude but we've had this concept in mind about a month ago for Myriad problem is, gps coordinates are fakeable so you're just gonna have a bunch of faggots draining your faucets via fake gps coordinate apps.
If you have a centralized database of user information, you could implement a number of constraints on faucet payouts to solve these problems.
For example, a simple heuristic would be to limit movement to prevent cheating.
In the world of programming there are few things that are not possible.
trust me we thought it over you can't as of right now come up to any solution to this, we thought about preventing long distances or time or something like that, problem is they can all be faked. thing is you're just going to have a server - client and the client will send the data over let's say rpc protocol, what's to prevent me from sending simulated data from my computer after analizing what my phone client sends.
also the word centralized goes against everything cryptocurrency stands for so any concept based on that is doomed to fail.
op, the discussion was on irc and it wasn't your exact concept it was something more elaborate and on a larger scale, if you want to talk join ##myriadcoin on freenode or just pm me here and I'll tell you all about it.
//edit: tomorrow, because it's 6 am and I'm heading to bed
