I remember being transfixed by Aussie50's clever hack of wiring his 12V CPU AUX power connector to an old school mechanical ammeter. Probably not a great idea today due to the intense power transients modern machines draw, but the idea of physical instrumentation on machines has always seemed like a good idea to me, if space is available. I like my gpu's coil whine, I can hear if it's running a misconfigured job. Human brains are amazing multi modal pattern matchers, it's good to let them do so.