Personal Heart Monitor

Every time I get heartburn, or not feeling well, I think of my mother. She went to bed thinking her chest pains were heartburn, and died in her sleep of a heart attack.
Well, I suppose she woke up, but there was nothing she could do apparently.

Does there exist a consumer-level heart monitor that could alert the user or a monitoring station when the heart starts misbehaving or even stops? I understand the user may not benefit from knowing their heart has stopped, but perhaps a caregiver, passerby, or even a smartphone app that calls 911.

I’d like to go watch the news, but want to know I’ll wake up for Jeopardy.