GPS data via tcp/ip

[pmichniewski]

This only mentions NTP functionality. What I am asking about is forwarding full NMEA sentences over the network.

I am not clear on why you need full NMEA protocol. If you use Flightaware, then you can set your location manually. Once set, there is no need to constantly update the PI location.
Tracking ADSB aircraft is not that time sensitive as it listens to the ADSB messages sent by the aircraft with accurate time stamps. MLAT needs to have the time more precise as you need to sync with other receivers to pin point the location of a MLAT only aircraft.
You can set you PI to sync from a number of NTP servers to update the time.

I only used ads-b as an example. I have many uses for having NMEA data available on my network, including ham radio related stuff. I just thought of it as a nice feature to have, since all of the required building blocks are already there. If you think that this is not at all useful, then I will shut up.