Reading Treks and Google Lit Trips

You might be familiar with Lit Trips.  Here is the definition from their website:

What is a Google Lit Trip? Lit Trips are downloadable files that mark the journeys of characters from famous literature on the surface of Google Earth. Along the way, placemarks with pop-up windows contain "just in time" resources including relevant media, thought-provoking discussion starters, and links to supplementary information about "real world" references in that portion of the story. Our focus is on creating engaging and relevant literary experiences for students. While I have seen these for a while, TeachersFirst recently shared their Reading Treks.  They look very similar (with a Google Earth file as well as directions) yet the stories appear to be for younger readers.