need an app for my apple watch very simle to just measure heart rate and beep

This watch app must monitor the heart rate sensor during sleep and after going over a certain BPM, the watch will start a vibration alert to wake up the sleeping user. The user can switch between sound alert or vibration alert. I don't need any special logos, icons, nothing. This is just a proof of concept. This is for when the user is having a bad dream.