PowerBlade

A paper detailing the design of PowerBlade and evaluating its performance was recently published at SenSys'15. The paper goes into more detail about the power supply and current sensing methods. It also compares PowerBlade to existing power meters across several household devices.

If you're interested, the paper is publicly available here: http://lab11.eecs.umich.edu/content/pubs/debruin15powerblade.pdf

Having difficulty with the longevity of the flexible tabs, we have implemented and evaluated a more stable method for making contact with the AC. The method is spring loaded "pogo" pins mounted in the plane of the PCB. These pins make contact with the AC prongs as they pass through (as the flexible tabs do as well) but since these spring loaded pins are designed for multiple insertions they seem to last significantly longer.