Wearable devices for activity tracking and gesture recognition have expanded rapidly in recent years. One technique that has shown great potential for this is ultrasonic imaging . This technique has been shown to have advantages over other techniques in accuracy, surface area, placement and importantly, continuous finger angle estimations. However, ultrasonic imaging suffers from a couple of issues: First and foremost, the propagation of ultrasound into flesh suffers greatly without a suitable coupling medium; Secondly, the complexity of the driving circuitry for medical grade imaging currently renders a wearable version of this infeasible. This paper aims to address these two problems by finding a rigid coupling medium that lasts for significantly longer periods of time; and devising a new sensor configuration to reduce the device complexity, while still retaining the benefits of the technique. Furthermore, a comparison between high and low frequency systems reveal that different devices can be created with this technique for better resolution or convenience respectively.