this video clip is from february but i just thought about it.
"Liat Ben-Zur, Senior Director at Qualcomm, believes that in the future, mobile applications will be able to bridge the physical and virtual worlds through augmented reality and contextual capabilities."
the clip and quoted text were taken from this site.
in the video they mention a super market as example. you could get additional information on nutrition or cooking instructions as well as advertisements for related stuff by facing your camera towards a product.
but there are also completely different possibilities to use such technologies. by implementing geo-referenced 3d buildings you could be able to see different states of a certain area during time. just imagine walking through a city like rome with your mobile phone in your hand. it could give you the possibility to see how the street you just walk along looked a few hundred years ago. in addition you can still get information that might be of interest for you (see layar or wikitude).
of course the same also applies for future projects or unbuilt alternatives that can be shown with such an application.
this is one of the areas i want to work on in the near future. so if you have any suggestions, ideas or critics(!) please leave a comment.