You can buy a cheap smartwatch that will monitor your pulse, give you a pulse oximeter reading, handle text messages and phone calls, take photos, and also within a reasonable margin of error check your blood sugar for about $35 on AliExpress.
What do you mean with that? Depending on the recency of your device they can be quite accurate. I use a Garmin though because they last longer on battery and are a bit more oriented towards sports and health. Some studies I found back then suggested Garmin is not that far off lab testing on most metrics. Yes even the guestimated ones like vo2max.
I mean what I said. There's a reason it's in their manual. And it's not in the back of the "legally cover our butts'" section. It's right next to the description of the feature itself