http://www.z4-forum.com/forum/viewtopic.php?f=2&t=14322
The app has been updated since the video was posted. Nothing but great reviews of the software. The wifi device looks big in the video, but it's actually pretty small and can be stuffed into the map pocket, etc.
The developer has a $10 off deal going on until the end of today, IIRC. The whole thing's pricey, but versatile.