I am looking forward to create a UiMagician binding for NEST users. At present UiMagician have binding for VSCP iot project.
https://sites.google.com/site/uimagician/
Please suggest right path for documentation for gateway agent so that REST communication can be establish to communicate with REST device.
Also if some reference example javascript code is available then please suggest the right link.
NEST home simulator does it create the virtual device or it create a HTML app to controll the devices.
https://developer.nest.com/documentation/cloud/home-simulator
The simulator is to create virtual devices for testing. You login with a new nest account and you can add devices and locations.
There are also Javascript code samples here
What you need to decide is whether you will do REST polling or have a real-time REST Streaming/Firebase.