My smart ring tracks my sleep stages, my continuous glucose monitor watches my metabolic response to a sweet potato, and my watch nudges me when my heart rate variability dips. I love all of it. And yet the single most predictive number for my long-term health — the one my doctor actually leans forward for — is completely invisible to every gadget I own. Blood pressure. It took an annual physical, a slightly elevated reading in a freezing exam room, and a nurse who said “you always spike in here” for me to finally close that gap at home. Six…