I love "silly" demos that combine technologies. Raul Guiu has written a very small app that uses the Mac's motion sensor to navigate around Google Maps. Now my first thought was "nice demo, can't see an application" then I started playing "follow the roads" which was fun for a short period of time. Now however I can think of quite a few bits where adding in motion and GPS could really commoditise certain areas. Take the "Fitness Watch" market, it costs £100-£200 for a watch and the "premium" ones are those with GPS. Now however with my iPhone I already have a GPS but I need to combine the information. The motion sensor could also act as a pedometer as well as indicating on a bike how fast I am going and what sort of lean I got into the corners.
This sort of "personal network" approach (which runs against the "one central device" theory) would give me all of the information I need (and more) and do so over a very limited area (I have them on me, if I don't then they aren't involved).
Its something that I expect we will see more of as things like the iPod/Nike link up are expanded and players like Polar want to get into the act. The key here will be around the short network comms and not burning the battery to get that done.
So yes its just using a Mac to navigate a Map, but it does go to show that not all Mashups have to be of web information. Mashing up personal information in a localised way can be just as, if not more, useful.