You can export all the data from Apple Health from a button in the app. It exports a zip with data in a usable XML format. The Health data is also available via an iOS API so there are apps available which pull and export the data in other formats (e.g. CSV). I try to connect any health related apps to Apple Health (e.g. Withings, MyFitnessPal) and use that are the central repository.

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01HNNWZ0MV43FF 2 days ago | parent [-]

I would love to try it but I'm guessing it won't work if I just buy a cheap used one and never attach it to an account and never bring it online?

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astrange 2 days ago | parent [-]

Not sure what you mean by "one" but a watch will work fine without a network connection. It does need to be paired to a phone.

It'd make it less useful as a watch though because the time will drift without an NTP server.

	▲	nerdsniper 2 days ago \| parent [-]
		I don't think this is true? All my Apple Watches refuse to provide any functionality at all, including just telling the time, until I pair them with an iPhone. This was an issue when I bought my first Apple Watch because I owned an Android.