REQUIRES IN-APP PURCHASE Vein Finder uses your iPhone's camera and torch to help visualise subcutaneous veins in real time — no special hardware required. Using published haemoglobin imaging techniques, the app processes each camera frame to highlight the contrast between vein-rich tissue and surrounding skin. Haemoglobin absorbs green light at 542 nm and 576 nm; by subtracting a scaled green channel from the red channel (R − s·G), veins stand out clearly against the background. • Real-time…