A wearable device supports continuous wearability and operation with a supplemental set of removable and replaceable batteries that recharge a first set of batteries powering the device. In an aspect, the wearable system includes a head portion coupled to an appendage of a user, where the head portion includes an electronic system powered by a first set of batteries, and a modular housing releasably engageable to the head portion that includes a second set of batteries. In this manner, the modular housing can be removed and recharged independent from the head portion, and then recoupled to the head portion to recharge the first set of batteries. Thus, in an aspect, the first set of batteries can continuously power the electronic system without a need for removal of the head portion. Such a system can be particularly advantageous for continuous, uninterrupted health and fitness monitoring.