Groupon offers the Emerson Sensi Smart WiFi Digital Thermostat for $89.99 with free shipping. That's $9 under last month's mention and the lowest price we've seen. (It's the best price today by $39.) This thermostat works with Amazon's Alexa-enabled devices via voice control and allows for WiFi control via Emerson's iOS or Android app. It requires two AA batteries (included).