I'm using a very cheap bluetooth gps mice and it works great with HLT.
I use RoqiBT4 that say bluetooth gps is working, and HLT see it as internal GPS!
So far nothing magic.
if you like to log also SATELLITE info you need NMEA data. Here I explain how to get them.
a) Configure RoqiBT4 as Generic OBD token (yes as OBD token not as NMEA compatible GPS)
b) Automatic paring on data request ON
c) in advance setting of HTL-> GPS Tweaks:
Speed Measured,
Custom Host 127.0.0.1
Custom Port 35000
Connection Type TCP CLient
These settings let HLT see your gps sensor as a generic WLAN sensor (Note you don't need a WLAN connection since it will connect locally to the iphone)
If you go in Satellite view you will see all the satellites

I hope you will find this tweak usefull.
-Salvo