Siri co-founder Dag Kittlaus has left Apple, AllThingsD reported on Monday. Kittlaus is said to have moved to Chicago to spend time with his family and to take time off from working. The report also notes that there are rumors Kittlaus is considering a new start up, though no details on the possible project were noted. Apple purchased Siri in April of last year and the software made its debut in iOS 5 during the iPhone 4S unveiling earlier this month. Siri allows users to interact with their iPhone to schedule appointments, check the weather, surf the web and more using voice commands. Reportedly, Kittlaus decided to leave Apple shortly after the iPhone 4S was launched while other members of the Siri team are expected to remain with Apple.