Show HN: I turned my iPhone and a $20 smart plug into an f-stop timer

A developer created Darkplug, an iPhone app that turns a $20 Shelly smart plug into a darkroom timer for film photographers, allowing them to control enlarger exposures with precise timing and advanced features like dodge-and-burn planning and split-grade printing. The app uses a red-on-black interface designed to safely work beside photo paper without fogging it, and works over local network without requiring subscriptions, with premium features available as a one-time in-app purchase.