In this study, we report on the fabrication of pressure/ temperature/ strain sensors and all-solid-state flexible supercapacitor based on a single common thermoelectric material of polypyrrole-coated graphene foam (PPy/GF) with a porous structure. For simultaneous detection of pressure and temperature without interference, a dual-mode sensor was designed where the changes of current and voltage could be measured, respectively, upon application of those impacts. The fabricated dual-mode sensor showed a high performance with a high sensitivity, fast response/recovery, and high durability over 10,000 cycles of pressure loading. In particular, the pressure was monitored using the thermoelectric voltage induced by the simultaneous increase in temperature via finger touch on the sensor. Additionally, a resistor type strain sensor fabricated using the same PPy/GF could detect the strain up-to 30%. In addition to those sensor decives, a flexible supercapacitor as a power supply could be fabricated with the electrodes of PPy/GF using its high surface area and psudocapacitance and gel-type electrolyte, exhibiting high electrochemical performance. Furthermore, an integrated system of such fabricated multifunctional sensors and supercapacitor showed the successful operation of the sensors with the power of the supercapacitor. This study clearly demonstrates that proper choice of a single functional material enables fabrication of both active multifunctional sensors for pressure, temperature, and strain, and supercapacitor as their power supply with a high potential application in wirelessly powered wearable devices.