During everyday office work we are used to controlling our computers with keyboard and mouse, while the majority of our body remains unchallenged and the physical workspace around us stays largely unattended. Addressing this untapped potential, we explore the concept of turning a flexible office chair into a ubiquitous input device. To facilitate daily desktop work, we propose the utilization of semaphoric chair gestures that can be assigned to specific application functionalities. The exploration of two usage scenarios in the context of focused and peripheral interaction demonstrates high potential of chair gestures as additional input modality for opportunistic, hands-free interaction.