the JetCat GPS is a little older design then the Eagle Tree and wasn't as popular an item so it didn't progress with technology and get smaller like the new ECU.

Spektrum has said they are coming out with the telemetry module that interfaces with the JetCat ECU, couldn't drag much more information out of Andy about it other then that.
their current setup does RPM/Temp/Batt voltage/Receiver voltage/Altitude/speed/etc..... so i'd hope their interface gave the same.