Thanks all for the info everyone - @MarkHunte your way looks interesting especially as I can send actual hype API commands which for my simple mind helps me make sense of it. I tried building your example Hypedocs and exported to MAMP but not much was happening.
I also have been messing with @Davirus's OBS graphics layer setup - which I have working but am scratching my head how it all comes together. It's quite nice as it runs a web server locally too and uses node.js. Theres a 2 second delay from pressing a remote button the slave(s) changing scenes.