[time-nuts] measuring currents on USB powered devices

[jimlux]

Any recommendations or brickbats for devices that measure the power 
drawn by USB powered devices.  I've been using a modified cable that 
breaks out the red wire to run to a meter, but it would be nice to have 
something that has a ADC and some sort of interface (USB?) that would 
make it possible to log the power draw.

I've got a bunch of wireless Beagleboards with GPS receivers and RTL-SDR 
pods (to do phased array measurements) and I'm trying to come up with 
better power information.

(the recent WiFi NTP low power discussion prompts this).

What would be great is if there were some USB "thru" pod that measured 
this and reported the data over a USB interface (recognizing all sorts 
of isolation issues that are possible), so I could plug the USB power 
"to" the beagle board and the USB power to the RTL-SDR, and log them both.