A limb movement biosensor for wearing upon a great toe or other appendage, the wearing upon the great toe being particularly useful for sensing dorsiflexion of the great toe as an indicator of contraction of a wearer's tibialis anterior muscle. A particular configuration of one embodiment allows for extended, multi-night data collection of limb movements by allowing an embedded microcontroller to sleep until movement greater than a pre-determined magnitude is detected by an accelerometer, by recording into memory such detection, while avoiding recording of the actual magnitude value of the detected movement. According to another optional embodiment feature, a light sensor is configured to wake up the processor from a lower power state, such as when a user removes the device from a light-protected package.