Has anyone on this board with a Garmin GPS V tried to interface with the GPS app on the empeg?

Yes. I only did it off the serial port directly on the empeg though to see the GPS app. On the Garmin, I went into the setup, found the serial out, and changed it to NEMA (instead of changing the GPS App to Garmin). It worked decently, but seemed silly to have it hooked up that way. I'll be connecting my GPS antenna to the car serial someday soon, once I figure out an easy way of running the wires where I want them.

In fact a lot of the satellite tracking status does not seem to be available in the documented part of the Garmin protocol, but is readily available in their NMEA output. The Garmin protocol is mostly useful to download waypoints and tracks off of the GPS receiver, but gpsapp doesn't use any of that.

The garmin and taip protocol decoders are going to disappear, they just aren't providing anything useful and any receiver that speaks either of these also has at least NMEA.