It's like a pedometer. It's an objective, no-guessing measure of your performance.
You can wear it for a few sessions, and you'll soon get to know how your cardiovascular system is performing with your activities.
You'll get to know pretty well, how your heart is working. You can even monitor how it goes back to normal, after a cool-down.
You might learn that you're working too hard in one area, maybe slacking somewhere else.
Soon it will have done its job, and you won't need it any more,.
There's nothing cooler than a reality check.
In business, they tell you "If you can measure it, you can manage it."