Earlier today I read an article on Micello on the Mashable site, it was one of those moments when technology really impresses me. I love those moments and recently there seems to be more and more things made in an attempt to impress people, and this can only be a good thing.
What Micello does is map out the insides of buildings, showing corridors and individual rooms then obviously uses your Iphone's GPS to tell you where you are in relation to everything else.
At the moment it is still very early days, apart from a demo (that caused a fair amount of buzz by all accounts) there hasn't been too much in the way of coverage for this. But hopefully it won't be too long before there is an app out that you Americans can play with (I can only assume it is launching in America first, then coming over here after some time).
Apart from the whole wow factor of being able to see inside buildings on your phone I think this could have a huge range of applications (these are off the top of my head);
I am thinking about people walking around schools on open evenings, each classroom could have a small blurb or a video about why that class is awesome - all accessible through a mobile device.
Meeting up with people at conventions and other large scale events could be made a whole lot easier.
There is also some potential for advertisers to get in there with some pretty cool mashups that could inform you of shops in the shopping market you are in that have sales relevant to your interests.
It is all very exciting and I can't wait to see it in action!