Not to throw the subject of the thread off...
If it is of any interest, I have a design that I kind of put on the back burner for a simple internal GPS module for the 15 and 996(XT) models. It would require internal installation and a single hole drilled in the back panel for an SMA GPS antenna connector. The power and data connections are all internal, drawing power from the scanner it'self.
I posted some info about it a year ago and the reception was lukewarm. I assumed it might have had to do with how new the 996 was at the time and the whole automatic position-based scanning scheme being a new method. Now that its fairly common place and there are plenty of units out there working, I thought it would be worth another mention.