Today only, Emerson Thermostats via Rakuten offers the Emerson Sensi WiFi Digital Thermostat, model no. UP500W, for $99. Apply coupon code "GREEN20" and checkout via MasterPass to drop the price to $79. With free shipping, that's $20 under our mention from two days ago and the lowest total price we've seen. (For further comparison, it's $16 cheaper than our Black Friday week mention, and the best deal now by $50.) This thermostat works with Amazon's Alexa-enabled devices via voice control and allows for WiFi control via Emerson's iOS or Android app and requires two AA batteries.