One of the goals of fusing GPS with mobile devices is "augmented reality" - i.e. the ability to map geo-tagged data over the real world in front of you via a virtual display.
Japanese cellcos NTT DoCoMo and KDDI recently gave industry watchers a taste of augmented reality apps for cell phones at Wireless Japan 2009.
DoCoMo showcased a prototype Android-based app that combines GPS data and a digital compass that knows which direction the user is facing, and feeds that over the network to a database to retrieve info on nearby landmarks and points of interest.
So, for example, if you're standing in front of Tokyo Tower, point your camera phone at Tokyo Tower, and icons appear on the screen pointing out nearby restaurants and coffee shops - as well as friends who might be in the area as well.
KDDI demoed a similar prototype augmented reality app that doesn't use a live video feed but uses recently snapped photos.
Neither has a set commercial launch date, but DoCoMo did announce a trial of its app with 1,000 users, according to IDG.