Built by a French company called Newscape, as a demonstration of its technology that allows mobile devices to process large quantities of data, Mobile 3D City appeared on our radar today via a video posted to design blog PSFK.
It appears that this app will cover just one city, and it certainly is a far cry from where Google Earth is today, but can you imagine if this kind of 3D experience was part of what Google's global ball of zooming, spinning and Wikipedia entries offered in the future? That would be pretty cool. It would likely take some serious, serious technology to be possible though. Thus the technology demonstration.