Diabetic foot ulceration is one of the complications of diabetes mellitus. One of the reasons of diabetic ulcers is neuropathy in which the nerves of foot are damaged and diabetic patients cannot feel the pain. Thus it is possible that they injure their feet without their knowledge and undetected injuries lead to the foot ulcer. Research works indicate that ulcers begin from the underlying tissue where soft tissues become stiffer. In this study, a wearable ultrasonic stiffness sensor for continuous monitoring of mechanical properties of soft tissue was developed and tested. The performance of the developed system was evaluated using soft tissue mimicking phantoms. In-vivo experiment was conducted while the participant was stepping. Pressure-displacement curve for plantar tissue at heel part was obtained for one compression-release cycle where certain tissue mechanical properties such as Young’s modulus and stiffness are computable.