The latest Apple and Samsung smart watches are all very good. I have the Samsung Galaxy 6, but the 7 is out and the 8 will be released in the spring...I think. Also, the Oura Ring does a decent job.

Less costly, and maybe something you'd prefer not to have to wear, is the Kardia Mobile. It's a small flat card pad you keep handy and you place a finger on each hand on two surfaces to get an ECG. You do this when you feel you might be fibrillating or having palpitations. All of these can send a graphic file to your computer or phone through the app, and you can send that to your electrophysiologist.