Earthscape has launched an application named Earthscape Basic trough App Store. It is an application very similar to Google Earth on normal computers like your PC or Mac. Altough it is not mentioned anywhere, it seems quite likely that the origin of the data is Google Earth.
The promotional video looks very promising, it seems to run quite fast on the iPhone. Many Wikipedia geotagged locations are linked to the surface, being displayed as a "W" icon. Tapping those icons will open the Wikipedia link in Safari.
This looks like a handy tool if you are somewhere unfamiliar and you ask yourself "What's that hill over there?". Well, pop up Earthscape and look it up! ;-)