I always like to build ridiculously powerful personal computer systems for myself. I was using a AMD 8350 8 Core System with 16GB RAM and 3x AMD 7950 Graphics Cards. When under full load the systems air intakes needed to be hooked directly into the output of an apartment window air conditioning unit to keep it cool. Due to the cooling requirments and the needed extra fans, the system needed a second power supply. (I was too cheap to buy a higher power one)
Given that the cooling fans and water pumps where running off a seperate power supply than the main CPU. It would be totally possible for the secondary power supply to fail causing an overheat condition and damage to the computer. I decided what was needed was to create an Arduino based system for monitoring tempuratures and fans not covered by the system, as well as shutting down the system in the event of a failure of the secondary power supply.