[Geojson] simple 3D geocode for AR

[Mike Liebhold]

A friend wrote me with a request for clarification on a topic we've 
discussed many times here,  but every time we've approached a consensus 
the answer seems elusive.

Many devleopers are starting to create applications for iPhones and 
Android phones to view location specific data  through the viewfinder 
using the -imprecise- capabilities of the built in gps and compass and 
applications platforms like Layar.

The question:

What is the -simplest- way to geocode a geoannotation in 3D using 
geoRSS/Atom, geojson, KML ....?

(Is there a practical reason why WGS '84 shouldn't be implicit, and a 
CRS  lookup NOT be required?)