Hi, sorry to hear about your fatigue. I did a quick google on "TBI cause of fatigue" and came up with a lot of hits but limited actionable information. The articles did identify different types of fatigue so it may be helpful to determine your dominant type of fatigue (or most problematic). Finding a tracker may require some experimentation on determining if there is something you can measure that correlates with your fatigue. Measurable things that come to mind are cortisol levels, HRV, attention, EEG frequency spectrum, blood sugar levels, nutrition/diet, sleep, body temperature, GSR, blinking, posture, grip strength, lung capacity.