Vonage says it has carefully followed all the rules in developing a VoIP-based application for iPhones and BlackBerrys that lets users save more than 50% on overseas calls to select countries. "It's an important first step for us. It moves us from the home platform. Over the long term, mobile is absolutely a critical place for Vonage to be competing," said CEO Marc Lefar. An In-Stat report predicts IP-based mobile technology has the potential to revolutionize the industry.