A recent post on Engadget is a good overview of Amazon Sidewalk. Worth a read if you have Amazon Echo devices in your home. This function will be enabled by default when Sidewalk is deployed.
Last year, Amazon announced Sidewalk, a shared network designed to keep your smart devices connected beyond the reach of the typical WiFi router. In order to do that, it’ll utilize certain devices as “Sidewalk Bridge” connections, such as Ring cameras and Echo products. Sidewalk isn’t live just yet, but the company has started informing customers last week that existing Echo devices will have this Sidewalk connectivity enabled by default. Amazon does note, however, that you can choose to opt out. And if you do so now, you can turn it off before Sidewalk goes live
Nicole Lee on Engadget