WagerWeb
Available on both Android and iPhone, the WagerWeb mobile website features a no-download mobile app that allows access to the sportsbook, casino, and account management services. Since it was designed in HTML5, the WagerWeb app is available even on old phones, from Android 2.2+ and iOS 3+. Though I was not able to test this, I expect that this mobile app will work on BlackBerry and Windows phones, as well.