That's an inventory of more than 300,000 apps available to 1m advertisers.
TechCrunch has seen a blog post that says AdMob campaigns will be added to the AdWords dashboard so that an advertiser can select the apps option, and then target ads at specific OSs, devices and app categories.
It also works the other way of course. TechCrunch points out that AdMob developers can also make their ad inventory available on the DoubleClick ad exchange.
This integration was always going to happen, from the moment Google spent $750m buying AdMob in 2010.
The self-serve dashboard approach made Google what it is today, so it's natural it would want to make mobile a seamless option for AdWords one million advertisers.
Google said: “(This is) the latest chapter in our ongoing efforts not only to bring AdMob’s and Google’s tools together, but to mobilise all of our ads products and services.”