By “realtime” we mean that our app doesn’t just simply download and display pre-baked OSM map tile images. Instead it downloads raw OSM vector data from our own server which has been specially processed and packaged into a very small and efficient format, and then it draws/renders the map directly on the device using an openGL ES based map rendering engine which we have built. This has many advantages, such as minimizing data downloads, much faster maps, various stylesheets, clickable POIs, etc… and the main feature of the app, to allow the user to pick as many cities, regions, or even whole countries as you want for download, and then be able to view these maps Offline.

I have added a short entry in wiki: http://wiki.openstreetmap.org/wiki/PocketEarth
More detailed information is available on our website: http://www.geomagik.com