A CPU does not wear down with use like a car engine does. Hence, a car has an Odometer, and a CPU does not. I does not need one.
But, just because it doesn't need one, does not mean it cannot have one! I decided to make one. World.... please meet the TurboLEDz CPU Odometer.
It uses the turboledz daemon for Linux to keep track of the jiffies (centiseconds) that were spent computing, aggregated over all cores. If your computer is idling, it ticks very slowly. If your computer is pinning all cores at 100% it ticks up very fast. The odometer value is stored in between reboots on your system.
I am selling it on my tindie store.