What they did
pentakkusu does darkroom printing and wanted a proper f-stop timer without paying a few hundred dollars for boutique hardware. His phone could do the timing; it only needed a way to switch the enlarger. He built Darkplug, an iOS app that controls a Shelly smart plug over the local network, with plain timing, f-stop timing, test strips, a dodge and burn workflow, split-grade printing with two timing channels and paper development timing. He says the app was blindly vibe-coded with Codex and Xcode. He wrote the post, answered the technical questions and sells a feature unlock for $25.
How it went
He has used it for months in an improvised bathroom darkroom. Measured with slow-motion video, switching is accurate to about 0.1 seconds, which he considers plenty for exposures of 4 to 60 seconds. It depends entirely on Shelly plugs; no other smart switch family is supported. The post drew 87 points and a long thread on timing jitter, red-on-black UI contrast and whether a custom ESP32 relay would be better.
Worth knowing
The app is the product of the agent's work, so the entry is really about letting Codex build a small hardware-adjacent iOS app end to end and then trusting it in a real workflow. Timing depends on the plug's network stack, so test accuracy yourself before relying on it. The $25 unlock plus a plug is still far under the price of dedicated timers.
GitHub