A hybrid system comprising a skin-conformal wearable supercapacitor (SC) and a strain sensor was developed. The system is based on thermoplastic polyurethane/reduced graphene oxide/polypyrrole films, surface-treated with iron(III)–(4-ethylbenzenesulfonic acid), and was found to perform well as a supercapacitor and sensor, with good biocompatibility. This device retains ∼99% of its initial capacity after 5000 cycles. This system will be suitable for skin-wearable smart electronic devices.