Watch Tuner 4+

Some experimentation will be needed to get the phone to best be able to hear the watch, i touched the crown to the phone mic, but once that is figured out it will read sufficiently well enough to get your watch regulated. Mine was slowing several mins daily and the beat error was hight (it gets roughed up). Now it is +/- negligible. Pretty surprised at the apps utility and effectiveness.

I just strap on the watch then slide the wired EarPod microphone between watch and my wrist. This gives instant readings of rate with my arm in each position - as if walking, reading, driving, typing.

If you just want to regulate a fast or slow watch, it’ll help. The readings can be inconsistent, definitely to do multiple tests to see if the app is reading correctly.

Use the mic on Apple EarPods headphone. The developers must have tuned the app for the Apple EarPods mic specifically. It did not pick up my lav mic at all, even when the mic was placed directly on the movement. Switched over to the EarPods and it started reading immediately.

Best results came from opening the case, and laying the mic directly on top of the movement.

Accuracy? Not sure, as I don’t have a timegrapher. From watching comparisons, seems to be in the range of the real thing. Probably say you’d want to add +/- 3-8 seconds to any reading.

In the end, it helped regulate a 1971 movement to within +/- 1.2 seconds (probably +/- 5-10 sec on a timegrapher) and now the watch actually keeps decent time.