I'm afraid that doesn't really help. I was hoping someone had actual experience with using devices like this with a Mac. Plus they seem expensive, but I have no idea what I should expect these to cost.
I use a LabJack U12 with their EI1022 Temperature Probe for temperature. You can get an AppleScript extension on the LabJack support boards and interface it with Indigo through AppleScript. It's not really a polished solution; it helps if you have a little knowledge of electronics and AppleScript, but it has been very reliable for me, and the LabJack can also be used to interface to other things at the same time. (I use it for direct HVAC control.)
There's also discussion of this sort of thing on Indigo's support forum. I know that there are scripts to get temperature data from X10 temperature sensors, for example.