I found this link on another post. I think this guy is 1/2 way there. Thanks to jbhodj & Drake!
http://www.ayefon.com/geo/index.cfm
Brettwurst, this guy's app is a web application which is inherently different. I think I remember him saying he was working on a native application, but I am as well
I'm not going to give a timeframe because I don't have a 3G phone (obviously) to test the CoreLocation services API. The iPhone simulator in the SDK has its coordinates locked at 37.3317° N, 122.0307° W (Apple's home campus in Cupertino, CA).
Hopefully in the next version of the SDK there will be a way to simulate movement. I've poked around the plist, app support, and binary files for the simulator but can't find a reference to how (or even if you can) change this at the moment.
I also haven't shelled out the $99 to test on a physical unit, so as time gets closer and we've got some better tools to integrate into the A-GPS CoreLocation framework and I actually get some code in decent shape, I'll apply for the developer/debug ability.
What features would you guys want in an iPhone Geocaching App?