I have some apps that use proprietary or special information from the NMEA data stream from my GPS, also there is AGPS which I can upload if I can link to the device. Would you consider adding a port where I can create a transparent TCP or other network connection to the bluetooth serial port (even registered only, maybe with the GPS app up with a switch in the on position)

I also realized that I have a 3d magnetic sensor as one of the options I merge into GPS data in one of the BT units. It also has accel and gyro, but the iPod Touch 4g has those but not the magnetic sensor. Would it be easy to add compass/direction/3d magneto to btgps?

CoreLocation has a "Coures" and a "Speed" field which I have to calculate from the difference to the last known location. If there is a standard reporting format for those, I'd be happy to directly use those instead of calculating them myself.

Extending BTstack GPS to act as a gateway to your Bluetooth device is too special. It probably would be better to have your app directly communicate with the Bluetooth GPS. I might help out with this, if this is for a commercial project with a budget. Please contact me by directly by mail matthias.ringwald@gmail.com

Issue 118 has been merged into this issue.

Course and speed should be part of the standard NMEA, though they call it "track". (sorry for the duplicate post - I spent too long yesterday tracking down a heisenbug). I know you have some of the NMEA docs but here is a quick reference:

http://home.mira.net/~gnb/gps/nmea.html#gprmc

Speed in knots and true course are shown. GPRMC is nearly universal. It has been on every GPS and I tend to use it for everything except Altitude which is in GPGGA.

http://home.mira.net/~gnb/gps/nmea.html#gpvtg

Less common but this is the track/speed specific sentence.