I'm considering using this wireless thermostat purely as a  remote temperature sensor (media equipment room and attic).  Does it link to ISY and report temperatures for both the internal and the external wired sensor or does it require acting as salve/master to a  wired thermostat to get information to ISY?

I can't comment on the actual question posed but do recall that this TSTAT must be plugged in if you want updates on a regular bases. Otherwise I believe it only updates when there is a change in temperature in a given period of time. There are a few threads about this issue and what solutions were provided.

 

It kind of defeated the whole *remote* TSTAT and being wireless since it was tethered to a AC plug!

The external sensor is only displayed on its LCD screen and not reported at all.

There is a thread here where the user. Disconnected the internal sensor and tied the external one to the solder pads the internal one was connected to.

 http://forum.universal-devices.com/topic/9152-how-to-monitor-water-temp-via-isy-and-catch-more-fish/