The development of new flexible and stretchable sensors addresses the demands of upcoming application fields like internet-of-things, soft robotics, and health/structure monitoring. However, finding a reliable and robust power source to operate these devices, particularly in off-the-grid, maintenance-free applications, still poses a great challenge. The exploitation of ubiquitous temperature gradients, as the source of energy, can become a practical solution, since the recent discovery of the outstanding thermoelectric properties of a conductive polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). Unfortunately the use of PEDOT:PSS is currently constrained by its brittleness and limited processability. Herein, PEDOT:PSS is blended with a commercial elastomeric polyurethane (Lycra), to obtain tough and processable self-standing films. A remarkable strain-at-break of ≈700% is achieved for blends with 90 wt% Lycra, after ethylene glycol treatment, without affecting the Seebeck voltage. For the first time the viability of these novel blends as stretchable self-powered sensors is demonstrated.