Question about temperature device

I've only been using the virtual switches up until now. Now for my dumb question: how are the temperature devices meant to be used (as opposed to just a simple variable)? I'm asking about this because I thought that maybe defining a virtual temperature device could allow Alexa to see the device as a thermostat, or something that could report and say the value (temperature or otherwise). This is something that's missing with Alexa: a way to have her say a number from a variable. This could be a temperature, level, percentage, etc. I tried creating a virtual temperature device and then adding it in the portal, but the device types offered don't include temperature or thermostat. I have Venstar thermostats and they do appear as thermostats, so the Alexa device type exists. It would be a great if a virtual device type that Alexa sees as a thermostat could be defined.