many of us looking to do this, affordably of course ... best option we've found so far seems to be some bulk-buy ADM1TEs connected to pulse-counting modules (not sure if the ODI is one of them) ... can't see it being affordable, though !
an alternative, though accuracy would not be so good, might be some CC128s, which can keep an eye on (IIRC) three circuits at the moment & may soon be able to do ten ...
other options include Plogg ...
Google'll find them all easily enough !!
any others, anyone ?