In addition to lighting control, Vantage (http://www.vantageinc.com/) makes a communicating thermostat that can directly control an HVAC system and is supported by the Domain Controller and the Ubiquity software.
This feature is now supported on the Domain 3000 in the 3.0 release for an additional software charge. Please email support@destinynetworks.com to receive the key to turn on this layer.