Earthcape developed a native version of Google Earth for your favorite phone/mp3 player/email/map/internet device (talking about the iPhone here!).
The demo (see video below) is of a mobile application in development that puts virtual earth software on the iPhone. The app runs locally on the phone, so you will have to download updated geo-spatial information over WiFi or 3G, which would take a ton of bandwidth and effect performance.
TechCrunch reports that:
What you see in the video is not Google Earth, although it looks very similar. Earthscape has created its own virtual earth program that it describes as a social geobrowser. As with Google Earth, it allows you to tag places with text, photos, restaurant reviews, and Wikipedia articles. It also lets you see different image overlays of the same spot during different seasons and different times in history.
The software is available only in private beta (sign up here).