Circuit Breaker current metering
Couple problems with that particular product. #1 it's $480.  #2 using it means you can't use an AFCI or GFCI breaker there, and you will need a lot of them in a rewire.  

The latest whole-house monitoring systems don't put a clamp ammeter on every circuit.  They put them on the main feed for that panel, L1 and L2.  They distinguish one load from another by the type of noise it places on the line, inrush current, interval it operates on, that kind of thing. They really don't care which circuit the load is on.  The installation is fairly neat.