HR-guided steady rides. Power-led intervals. No account, subscription, or server.
A smart trainer can hold a power target to the watt. The problem is that the watt is not the workout. The same 180 watts that felt like an easy aerobic ride in the first ten minutes is a different physiological cost forty minutes in, when your heart rate has drifted ten beats higher for the same effort. Zone Pedal is built around that gap. On supported steady workouts, it watches heart rate over Bluetooth and adjusts compatible smart-trainer resistance when the trainer has room to respond. Short intervals stay power-led with heart-rate guardrails, and floor-limited easy rides are labeled instead of reported as clean control. It is an iPhone app, a one-time $29.99 purchase, with no account, no subscription, and no server. The math runs on the phone and the data stays there. You need a Bluetooth heart-rate monitor and compatible smart trainer to use it. You do not need either one to find the control problem interesting.
Plain facts: Zone Pedal is available now on the App Store for iOS. It costs $29.99 once. It needs a Bluetooth heart-rate monitor and compatible smart trainer. There is no account, no subscription, no server, and no cloud copy of the ride.
The honest version of this project is shorter than the ambitious one. There was a weekly adaptation engine, a readiness questionnaire, cloud sync, accounts — all built, all working in tests, all cut. Not because they failed. Because none of them improved the ride that was happening right now, on this device, with this body, and every one of them added a server, a privacy policy, and someone emailing me because their workout disappeared in a tunnel. The interesting part was never the platform. It was the body in the loop.