Device to monitor irregular heart beat.

I am suffering with atrial fibrillation and grave hyperthyroid for 15 months. Both were diagnosed same time in december 2020. Recently i  got holter test for 24 hours which was normal with no atrial fibrillation recorded in 24 hours. But i do get high pulse once in 1 to 2 months just while i sleep. Please suggest if there is any smart watch with ecg feature available in market which is compatible with realme gt neo2 android phone. Or any other device available to check ecg or irregular heart for long period which is affordable. Holter device i cant use for long time as it cost Rs 3000 per day. My medanta doctor suggested to use device for long period as i get high pulse in  1 to 2 months. They may as stop blood thinner if i dont get irregular heart beat for long time.