I am sorry for the confusion about how to control your thermostat while away from home. You will need to purchase an Alexa compatible Thermostat, which may or may not require a hub depending on the brand and product.
Hello Forum people, My name is Zach and I am a Moderator for Amazon. I enjoy Film Making, Graphic Design and Web Design in my free time (Different than Kindle Freetime of course). I am also an avid adventurer, looking forward to my next outing!
Any Smart Device you purchase will have a companion app that you must download to your smartphone or Tablet. Which you will be able to control those devices remotely. Some of those devices you will be able to control using your Echo, even a few might allow you to control the devices using the Alexa app. But you are better off using the companion app while away and using Alexa when you are at home. As for Hubs yes some not all Smart Home devices will require a Hub. There are a slew of Smart Home Devices that are compatible with Alexa just check out this link