  In the rapidly growing field of wearable technology, optical devices are
emerging as a significant innovation, offering non-invasive methods for
analyzing skin and underlying tissue properties. Despite their promise,
progress has been slowed by a lack of specialized prototypes and advanced
analysis techniques. Addressing this gap, our study introduces, HydroTrack, an
18-channel spectroscopy sensor, ingeniously embedded in a smart-watch.
Accompanying this hardware, we present signal processing and data analysis
techniques implemented at the edge, designed to maximize the utility of our
system in comprehensive health tracking. A pivotal application of our device is
the real-time assessment of hydration levels in physically active individuals.
We validated our prototype and analytical approach through experiments on six
participants, focusing on hydration dynamics during physical exercises. Our
findings reveal an accuracy of avg. 95% in determining hydration states.
