Luna have been teasing a new feature this week - and today left a screen of a slack chat in a screen shot with the following url http://astro-hq.com/luna-mac2mac/
You can new use another mac as a secondary display as well as the iPad!
Looking forward to trying it out 
Starting to think about picking up a Luna Display prior to a business trip next week. Intrigued by the idea of turning the iPad into a touchpad entry for the Mac.
Okay this might push me over the edge.
I have yet to try sidecar but this looks promising.
They’ve done such a good job of keeping this secret that there seems to be no information out there about how it works or where to see a demo.
I guess the idea is that you have an iMac and a MacBook of some sort and want to use them together?
Clever, I guess, but I can’t see a lot of people using it.
it’s not officially released or announced yet, i just noticed the URL in the screen shot.
I’m looking forward to trying it out when I get home - my HDMI monitor has a lovely pink hue and is unusable with my MacBook Pro.
Possibly save me £££ on a ultrafine for the few days a week I will use it.