Polar M200 is focused on running GPS watch, but one with optical heart rate, smartphone notifications, and even structured training options.
It’s a very easy to use and it only has two buttons, but it doesn’t have a touchscreen. If you want to access Training, Activity Tracking, History, My HR, and Settings, just press right button.
Heart Rate is not for 24/7 use, but you can use “My HR” to check your heart rate at any point.
Here are some interesting videos: