According to The Verge:
Both companies' Wi-Fi-connected thermostats, which are usually controlled by smartphone apps, should work with Alexa by the end of March, Amazon says. Alexa will also start working with some of Insteon's smart home thermostats, too.
Amazon just announced two more Alexa devices, the Echo Dot and the Amazon Tap that should be able to control those thermostats alongside the Amazon Echo.
Source: The Verge