I've done a number of control systems for high-end audio loudspeakers, which perform the following functions:
One subwoofer also has a front panel display and an infrared remote control, allowing the user to select a gain setting, and choose from preset room equalizations or a custom 7-band equalizer. A "hidden" service function allows a tehnician to perform diagnostic function and update firmware.
Another speaker without user controls can peform firmware and DSP updates via the audio input, with feedback from the LED power indicator.
Currently (2018+) working on a set of paired wireless desktop speakers, Master unit sources from Analog & Digital inputs, Bluetooth, Streaming services or Chromecast audio. Slave pairs to master via low-latency wireless radio. Both speakers have keypad/display and can be operated identically from either unit. I/R remote control is also provided.