Streamers sometimes use a heart rate monitor widget on stream. There might be multiple solutions here but checking out pulsoid.net it seems like a free solution can be made here if it is compatible with the smart watch used. Android app to webpage might be possible with setting up a local host server. Don’t know what it’ll do to the battery life of your watch and if the widget works without OBS integration. Maybe someone familiar with this can weigh in?

Never heard of this, but you are likely to be deemed at fault due to reckless driving above certain speeds.