It would be exceedingly easy to make a plugin that turned on or off a tally light like a usb blink(1) based on status of recording/streaming, and set the light color based on different status etc.
As long as you have an api to turn the lights on or off, it's very easy to react to OBS signals that are send when broadcasting/recording starts and stops.

People don't know but when donationcoder was being first experimented with in 2003 or so i think, one of the main features on the previous version of the website was a programming school section where people could see assignments for ideas to program and submit their implementations to move forward..  This was before all the great professional programming teaching websites came into being which do a great job of encouraging new coders.  It was very primitive but some people had fun.