I came across a very insightful article by Bill Buxton in Business Week called The Long Nose of Innovation which basically argued that innovations which make a difference are in fact based on technologies which have been around for a while. Buxton argues that innovation is really about the application of things already in existence as much as it is about inventing entirely new things.
This resonated with me as I thought about something Ray Kurzweil, the futurologist, said in a recent lecture (which I can't now find!). He argued that since technology is growing exponentially, if you are building something (in his case computer translation software) you should design for what computers will be able to do by the time you are ready, now what they can do now.
It seems to me you could distill some good advice from these two: look for technologies and capabilities that are around now, but which have failed to reach their potential because computers or mobiles aren't powerful enough - then design something which will be truly impressive once the power catches up - which it will.
Augmented reality - likely to be all the rage in 2010 - falls into this category. The technologies have been around for ages (camera, compass, GPS), but it wasn't until they were combined into relatively cheap, powerful phones like the iPhone and Android that they could take off.