This is a StreamLabs OBS app which polls the StarCraft II Client API to determine what the current streamer is doing in StarCraft (In game? In a replay? Out of game?) and transitions to the desired scene.
Add the app in StreamLabs OBS and run the program to proxy requests. You can
download the proxy program here. It will run in your system tray with this
icon: 
.
You'll probably get some security warning about untrusted code for the proxy. If you know how I can solve that for people let me know!
Streamlabs OBS apps are served as HTML/JS on a different origin than the
StarCraft II Client API, so we're forced to respect CORS. I'm unsure
of any way of getting around this other than having a program proxy requests
to the StarCraft II Client API and adding the header
Access-Control-Allow-Origin="*" to the response.