Commercial equipment that does the same thing costs tens of thousands of dollars. There is a new generation of chips arriving now that output the raw satellite data and allow you to do the calculations yourself, which allows you to tweak the sources of various kinds of data. For example, you can get better ephemris data from NASA than you can from the satellite broadcasts.. you can also exclude satellites with marginal or reflected signals from messing up your 3d fix. I would imagine it would be really cool for cyclists. I know tha when its a little further along I am going to try logging rides. Basically, they should look like a GPS track you see now, but hopefully the tracks should be more accurate, by a very good margin.

The antenna has been the thing that is hard to get right. But we're making a lot of progress.