Since it's unlikely that Amazon's security is up to par with Apple's, a good middle ground would be an application that always ran and was always sniffing the E

Since it's unlikely that Amazon's security is up to par with Apple's, a good middle ground would be an application that always ran and was always sniffing the Echo traffic, and would keep a log of when the Echo was sending traffic out of the network. Maybe it alerts you when it is sending traffic. Then you can compare the times it was talking to Amazon vs when you were talking to the Echo and figure out if it communicates without you.