Social networking platform Twitter says its MoPub ad network now reaches more than 1 billion iOS and Android users every month, and so on Monday it is making its latest move to build out that mobile advertising business with more products. Twitter is kicking off the global rollout of mobile app promotion ads — units that either take users to app downloads, or to the apps themselves if they’re already installed, via a deep link. Along with that, Twitter’s unveiling new cost-per-app-click pricing for the unit and a dashboard to track usage. CPAC pricing basically means a publisher will only be charged when a user actually goes to the App Store or Google Play from the ad, or when the user opens the app directly from Twitter. Mobile app install ads have been running in beta on Twitter since April this year, and the company has been talking about them for much longer.