The cRIO and the cDAQ platforms have different application spaces: the cDAQ is great for simple data acquisition applications when you just want to acquire data with a Windows PC, and the cRIO is great if you need an embedded solution that can run headlessly without being connected to a PC, or if you need the determinism and performance provided by a real time processor and an FPGA. If all you want to do is monitor power levels from a windows PC, the cDAQ may be the best solution for you, but you can certainly monitor power from the cRIO as well if you already have that hardware, or if you have the need for an embedded solution/determinism/higher performance.
Power monitoring on the cRIO can be performed with the same C-Series modules that Hooovahh mentioned, and the documents he linked give a good overview of the process.
Regards,