Keep a Close Watch on How Hot Your MacBook Gets

SensorX is a tool that watches historical and current processor temperature extremes. When the temperature crosses the upper limit, the program notifies you of the same through a message and/or sound. SensorX shows current minimum and maximum temperatures, and average and past temperatures of cores. It runs silently in the background and can be accessed from the menu bar. Moreover, the display alerts and modes are configurable, along with the update frequency.