At a Google I/O developer conference keynote presentation today, the company revealed that 100 million Android devices have been activated worldwide, and introduced a new open accessories initiative with gaming applications.Stressing Android's momentum in the marketplace, Google's director of product management Hugo Barra pointed out that there are now 400,000 Android devices being activated every day, up from 100,000 per day a year ago and 300,000 per day in December Thirty-six manufacturers have made 310 distinct Android devices, which are being supported by 215 carriers in 112 countries, Barra said. Those devices now support over 200,000 apps from 45,000 developers, which have been downloaded 4.5 billion times overall, including 1 billion downloads in the past month, he said.The presentation went on to show off a new Open Accessory API, which lets Honeycomb and Gingerbread-powered Android devices work as USB hubs for external accessories.The demonstration included examples of an Xbox 360 controller being used to control a game on an Android tablet, as well as an exercise bike being used to control a simple game on an Android phone.Android accessories don't require approval from Google or any device makers, and can automatically direct users to necessary apps upon hookup. While only USB connections are currently supported, support for wireless accessory connections through Bluetooth is coming in the future, according to the company.An Arduino-based Android Device Kit will also let developers use Android devices as controls for other devices -- a demo showed a tilting tablet controlling a large, servo-powered Labyrinth board . A separate [email protected] initiative demonstration showed action in an Android game ofbeing synchronized with specially designed LED lightbulbs in the room.Google also announced a new partnership to get Android updates to users more easily, with major U.S. carriers including AT&T and Verizon pushing free OS updates to new devices for 18 months after the initial purchase.