Quick update, yes you can measure the transmission temp and a whole host of other stuff. In the Transmission Control Module alone there are 55 different measurements,
- Transmission fluid over-temperature counter
- Engine oil over-temp counter
- Transmission output shaft speed
- TRANSMISSION OIL TEMP
- Turbine speed
- Shaft torque
These are just a handful of what it can read, in the engine (powertrain) module there are over 250 different measurements. It's a decent bit of kit, I wouldn't be without it.
You can also save the results to memory card (32GB card was included with mine), or you can plug it into the computer to power it up and read the logs. Pretty easy to use.