No wearable that I know detects sleep apnea. They can monitor your heart rate and rhythm, and they can monitor your blood pressure, and they can monitor your oxygenation, your 'sat', or O2 saturation levels, including while you sleep. My Galaxy, in Canada, was finally approved to measure for AF via an ECG, and it even had to be approved by Health Canada for measuring the blood pressure (BP). I don't know about how it currently sits in the USA, but a quick search on the www should have an answer for you. Or ask the sellers.

My watch, through a phone app (on and listening while I sleep), will report snoring, which is only a loosely associated indicator of sleep apnea. Some snore and sleep properly, some don't. Those who snore and don't probably, not certainly, have some form or level of sleep apnea. But, the SO@ levels, if they show a marked dip at any point in the previous night's record, you can take that to the bank...it's an indication that you had a apneic event or somehow stopped breathing...which could mean a central apnea , or when the brain forgets to make you breathe. It's worth investigating, especially if it comes about each night, especially more often as time goes on.

Remember, though, that there are other devices such as wearable SO2 meters that keep a record of your sat levels, and there's the Kardia Mobile device, only a few dollars, that gets really strong reviews, a device that also keeps downloadable records for your night's data. The Kardia is only for heart rate and rhythm.

BTW, and I don't know if this is just a Canadian thing, I would think/hope not, but my Galaxy watch must be recalibrated with a suitable sphygmomanometer every 28 days. You'll get a warning that the calibration period is about to lapse, and you have three days to recalibrate. After that, when you go to use the watch to measure your blood pressure, you'll get a flag saying you must recalibrate...or else.