This is the most unusual health tracker I've seen yet, but the design makes surprising sense

Petal is a discreet health-tracking bra insert that uses bio-impedance sensors near the heart to monitor menstrual cycle changes, heart metrics, body composition, and hydration, aiming for more accurate readings than typical smartwatches. Made with biocompatible materials, it fits in one size, lasts up to 18 days per charge, and is positioned as a subtle alternative to wrist- or finger-worn wearables. The device ships in May in black and blush, with pre-orders available at a discount.