Speedfan got a lot more functions than you might expect.
The user interface isn't pretty but functional.
The small tools allows you to supervise the speed of your fans and if necessary to regulate them yourself. It is also able to read miscellaneous sensor data. Thus you are able to keep an eye out for the temperature and voltage of your devices.
The new version 4.35 changes many little details and new hardware is supported. A full changelog can be found here. Speedfan is available from the developers.