Whether you're a tinkerer with a custom rig, or you just aren't sure why your computer's fans are running, checking your CPU usage is a pretty common task. Instead of using a boring on-screen activity monitor though, you can hook up your machine to a car tachometer for constant feedback.
This hack comes courtesy of ivancreations, who created an entire PC monitoring block from real-world components. The full instructions are on his blog and needless to say, they're pretty complicated. If you can makes heads and tails of his plans though, the results speak for themselves.
While the tachometer is my favourite part of the build, he also wired up some LED light grids to illustrate other vital system information as well. If you think you're up to it, or just want a closer look, be sure to check out the source link.
Real Computer Monitoring Block [Ivancreations]