Rays features an advanced outdoor detection system that intelligently combines GPS accuracy analysis, movement pattern recognition, step analysis with treadmill detection, location context understanding, and light sensor data (when available). Our personalized machine learning adapts to your unique routines and frequently visited locations for improved accuracy over time. Your privacy is safeguarded through geohash clustering technology for weather data, while precise location is used only for accurate outdoor detection. You maintain complete control through standard iOS/Android location permissions, and the system runs efficiently in the background without impacting battery life or requiring manual tracking.

Our algorithm analyzes your skin type (Fitzpatrick Scale I-VI with research-validated synthesis multipliers), age (accounting for synthesis decline over time), geographic location (latitude adjustments and seasonal UV variations), current supplement intake, and lifestyle factors. Based on Endocrine Society Clinical Practice Guidelines, we provide recommendations as precise as your doctor's, but as convenient as checking the weather.

Receive personalized guidance like 'Get 18 minutes at 11 AM tomorrow' based on real-time UV index, cloud cover (10-90% reduction factors), solar positioning, and your personal synthesis rate. Our intelligent engine analyzes current vs. optimal timing and may suggest waiting for better conditions when UV will be 2-3x more efficient for vitamin D production.

Monitor your vitamin D synthesis with detailed weekly charts, streak tracking, and comprehensive health insights. Our calculations model scientifically-proven synthesis saturation (why production plateaus after 15-30 minutes) and automatically adjust for seasonal variations. Rays seamlessly syncs with Apple Health to integrate with your broader wellness data and prevents excessive total intake when combined with supplements.