I don't know of a program that monitors fan speeds other than speedfan, and the ones listed, or your motherboard software.
But I was just going to comment that you should never put faith in ANY program that monitors voltages. They are wildly off and usually mis-calibrated, if at all. The only good they might do is tell you if you've got say: 12 volts versus 7, or 5volts. But if you are trying to gauge between: 12.0V and 12.2V or 11.7 and 12V, there is not way they are accurate enough for that. The reason is, they most likely use a low level, small resolution ADC and comparator to "monitor" voltages.
If you are concerned enough to worry enough about voltages, the only way you are going to get accurate and reliable results is with a digitl multi-meter.
Edit: Sorry, maybe I misunderstood... Are you talking about CPU, RAM, and Northbridge voltages, or PSU voltages?
Yep, those and PSU voltages (alittle more than what Asus Probe offers, yet more accurate [on die temps, for example]). Need to monitor the temps and volts because of past bad experience with motherboards dying. It just needs to be accurate enough to warn if the rails drop too much (as I'll be adding more hardware later), and if the temps after playing a game for 4hrs is within limits.
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