Certain embodiments of the present technology disclosed herein relate to implantable systems, and methods for use therewith, that use a temperature sensor to initially detect an onset of patient activity, and then use a motion sensor to confirm or reject the initial detection of the onset of patient activity. Other embodiments of the present technology disclosed herein relate to implantable systems, and methods for use therewith, that use a motion sensor to initially detect an onset of patient activity, and then use a temperature sensor to confirm or reject the initial detection of the onset of patient activity. The use of both a motion sensor and a temperature sensor provides improvements over using just one of the types of sensors for rate responsive pacing.