This work presents the design and the realization of a flexible front-end circuitry for electrochemical sensing with wearable devices. The hardware combines readout circuitry for amperometric and Open Circuit Potential (OCP) measurements. The sensing platforms are dedicated to lactate and lithium detection in sweat, hence allowing the monitoring of athletes under physical effort. The wearability of the system is ensured by the flexibility of the electronic substrate, its small dimensions that fit an armband case, and the wireless transmission through a Bluetooth Low Energy (BLE) module. The power consumption of the system has been evaluated to be 200mW, with 3.6V on board power supply.