On a recent project I needed to fairly accurately measure current and power consumption of a handful of parts in real time. We needed to measure current in the range of micro amps, so this was actually somewhat tricky.
I could have just used a bunch of super expensive current meters, but I managed to find a much more convenient and cheap solution using a Raspberry Pi. We were already using a Pi to allow for remote debugging, so I went looking for something I could hook up to that.
I found these ADCs:
They plug right into the GPIO headers on the Pi and even come with some python libraries for reading them.