Mobile social gaming startup Frengo, which is backed by $2.3 million from Index Ventures and Khosla Ventures, is officially announcing its service today. The company creates games based on SMS and the web, with themes like March Madness-style polls, make-your-own text quizes (which are actually pretty fun) and MySpace mobile text services. Danny Rimer and Vinod Khosla back SMS games? — go figure.