Scott - Scangauge's response to my inquiry was that "there's a good chance" it would now monitor ATF temp on 05 and later Toyotas using this XGauge:
Transmission Fluid Temperature
TXD: 07E021D9
RXF: 032180000000
RXD: 2810
MTH: 00070065FE70
NAM: TFT
But that's not exactly a vote of confidence. It's great if I get a temp display in the unit, but I personally will have no way of knowing if it actually represents the ATF temp. Do you remember if you ever tried it?
This same XGauge is posted here, so that is encouraging:
http://www.scangauge.com/support/toyota-specific/
...but someone on another forum reported it didn't work on the 06 Tundra. But you might try it on your Tacoma if you haven't already. Maybe its computer is slightly different and it would work.
Dave