I’m surprised I didn’t find anything going about this in the forum.
My echos and dots started working with the drop in feature for device to device last night.
Simply name your devices what you want… ie "kitchen"
And then just say, Alexa, drop in on the kitchen.
Two voice communication from one device to another.
You can call a single device as well.
I couldn’t get it to send a message to a single device yet, but so far I’m really liking the new features!