I use the kill-o-watt meter. It works quite nicely.
But if your looking for software, the only thing I know is perhaps speed fan or HD monitor where it shows the voltage on the different rails.
Other then that, I don't know of any software that would give you wattage readings for a particular piece of hardware.
Forgot to mention, even software that reads voltage are not totally accurate.
You will need a device. There is no software capable of measuring individual real time wattage used by individual components comprising your system. Hardware will be involved.
Unless video card manufacturers , for example, would include some kind of 'hardware' wattage measuring device on the actual card and then a software became available to monitor that installed hardware device, that kind of 'power' usage monitoring is not possible. Of course, I would pay $13.99 for a kill-o-watt device and know how much wattage my system is using at any given time before I would pay $1700 for a wattage-monitored enhanced Radeon 1550. LOL.
Watt am I saying, I have a Kill-o-watt device that is capable of telling me how much 'power' my system is drawing at any given time.
I believe the kill-o-watt measures the amount of wattage the PSU is putting out at any given time.
I like this one, this is what I use to see my readout of my Wattage usage, and it also fan controls 4 case fans and looks nice.
That's a nice controller. If you download the product manual and look at the large main diagram you will see the unit has an adapter to connect directlty to the PSU to monitor power consumption levels. So, this unit does the same thing as the kill-o-watt ($13.99) which is to measure the power consumption of the power supply and at that point. The unit does not measure the power consumption of individual compnents of the system. Pretty nice unit. I like it.
You can find this information I am referring to by downloading the product manual here: