I took my a while to discover how they did the telemetry, but it appears that used the Argos System which is a a satellite-based system for very remote telemetry: http://en.wikipedia.org/wiki/Argos_System
That's quite the story, I'm no longer a kid so 'science news for kids' will have to do with a stow-away from now on.
Excellent article and a really nice accomplishment, especially the modifications to engine and fuel to make it that efficient. Is there more detail available on the guts of the plane ?
This is impressive, but I think there's a point where something is no longer a "model plane" but a "UAV". And I think that point might be when it has autopilot. A really cheap UAV, which is a pretty cool idea IMO.