In this work, a wireless compact general-purpose electrochemical biosensor system was designed for continuous health index monitoring in implantable and/or wearable devices. Two different modes, the SCAN mode and the COLLECT mode, are applied in the proposed design. During the SCAN mode, the redox potential is optimized to improve the robustness of the COLLECT mode by enabling a relatively high amplitude of the output current design. The total weight is 4.5 gram including a 0.5Wh Li-battery, which can be applied to freely-moving small animal subjects for over 24-hour. The Experimental results shows a linearity of 0.9997, and a sensitivity of 2nA. Nitric oxide and Nitrite are used to demonstrate the concentration of the proposed system. In-vivo experiment was applied in the joint cavity of the New Zealand white rabbit.