This thesis introduces BioResonant interfaces, which bidirectionally communicate with the user's body to provide information on their physiological state. This facilitates regulation of their stress levels and ultimately a more mindful daily life. Based on the principle of respiratory sinus arrhythmia (RSA) and physiological synchronization, the BioResonant interface is designed to stimulate at the subconscious level using subliminal tactile biofeedback. Through this process, the user's physiological state can be aligned with their desired state. I present three different forms of the BioResonant Interface, a wearable device, a cushion, and a kinetic display, which utilize either heart rate (HR) or breathing rate (BR), or both. I present their fabrication, design, and evaluation method in the following interaction scale order: local interaction with the skin; general interaction with the body; and embodied interaction with the environment.