Edit: reading further in the thread, this comment said it better than I did (though they aren't speaking about the video, it makes the same argument):
https://news.ycombinator.com/item?id=19409734> It should be noted though that this study does not say that an Apple Watch will overall provide medical benefits. It also doesn't follow automatically from the fact that it detects things with a certain reliability.
The interactions of early detection and medical benefits and downsides are complicated and it will require a lot more science to figure out whether a device like an Apple Watch can provide benefit.
The only thing I would add is the last thing I mentioned in this comment, namely that you might consider buying one for a higher risk person like your grandpa rather than yourself.
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Watched the whole thing, basically the argument is that overdiagnosis leads to people worrying (increasing stress) when the doctor says "based on this I can't give you drugs since the drugs aren't completely harmless", or the doc might recommend follow up tests that give ambiguous results and escalate (in the example) to an operation to test a certain thing where the patient has a 1 in 3k chance of dying from the procedure itself. Additionally, experiments where they strap a bunch of such devices to healthy patients (basically what apple's watch does as well, especially the young and modern people will buy it) and while it lead to more diagnoses, it didn't decrease the chance of stroke or heart attacks in that group.
I don't think any of this is a significant reason not to buy it. I'm not going to buy one for various reasons, but this isn't one of them. It is good to be aware of the arguments, though: it might lead to someone buying one for their grandma rather than healthy and young(ish) self.