I need a design for current/power measuring/logging.  I would like to
measure the current and power usage for my 20 houshold circuits.  I
would like to use some sort of current sensors that wrap around each
current carrying wire, rather than any devices through which the
current must pass (shunt resisters, etc).  I would like to log this
data within a powered device, and transfer the logged data to a PC
periodically (once per week or so).