Yes—Apple Watch records your heart rate every 10 minutes during the day, and every five seconds when you put it in workout mode.

For example, here's what my heart rate looked like during the Game of Thrones finale: https://cardiogr.am/c/gameofthronesfinale

It captures heart rate at a much lower rate unless you indicate you're working out, so I guess if you knew it was getting to breakup stage of the conversation you could ask them to wait a sec while you start your workout