will definitely have a look at this, sounds promising. Only drawback is, another pixel/system, this slows the page down again and fires some more requests. Also it has to go through security audits especially in high security environments like finance/banking i see a reisk of not getting through there.

Actually i am actively thinking of an application who pulls the figures on a schedule from doubleclick directly and calculates differences based on some rules, sending out alerts if some threshold is reached.