Doctor Mom has managed to add her Sonos to the Amazon Echo by installing the Sonos Skill and letting it discover them in the devices section. It does have limitations, though. It can't play Spotify or Audible. The Echo will also immediately turn off all the speakers when it wakes up. The Sonos skill isn't really ready for prime time just yet. That's why she recommends getting the Vaux External Speaker for the Echo Dot, because you can drop the Dot right into it.