Recent research studies have shown the serious health risks associated with prolonged sitting. Standing up and walking on a regular basis has been proved to improve an office worker’s well-being. Small behavioral changes like the aforementioned are the basis of preventive medicine and even though they appear easy to follow, in practice are difficult to apply. Advances in technology miniaturization and smart sensors are paving the way for the development of devices that empower preventive medicine. These devices use the power of persuasion to help people change behavior and maintain well-being. They act as an ambient personal “coach” that monitors and intervenes at the right time. In this paper we present the HealthBar, an ambient persuasive device that helps users break up their prolonged sitting habits.