I had the same question. I’ve been designing a device to do that with an Arduino (microcontrollers that people who like electronics play with). I’ve been tracking my heart rate at night with a wellue ring so I know I’m never above 100 (actually 85, average is 43) if I’m not in afib. I’m using a heart rate sensor that will fire a buzzer if my heart rate goes above 100 for more than 10 seconds. I’m a terrible programmer and haven’t settled on a design yet. My wellue ecg device can be programmed to buzz at different heart rates but I don’t like sleeping with it on. It is useful when I’m in afib. My ablation was may 6 and so far no afib. I’m feeling so much better. My Apple Watch told me my walking HR was 74 before my ablation, now it is 64 and I walk faster. If your heart rate is all over the place at night this wouldn’t work.