Amazon has launched a simple way for users to sign into apps and make in-app purchases with Login with Amazon, a new single sign-on service that works with all of its users’ accounts. The system works like Facebook Connect and Google+ Sign-In, allowing users to click a button and enter account information that they already know to quickly create a profile on a new service. Amazon has already been testing the system with two of its subsidiaries, Woot and Zappos, and it’s now opening up the program for all developers to use across the web, iOS, and Android. Though Amazon isn’t allowing all of those sources to utilize its customers’ account information to facilitate purchases, that option will be available for purchases made within games and apps.