Smartwatch/Wearable experiences

I'm looking into getting a smartwatch to help me track my heart rate, and hopefully help me remember important tasks. I was hoping that I could get feedback from others who have tried using a fitness tracker or smart watch to help with managing ADHD. What worked or didn't work? Do you recommend a certain wearable?

My priorities for a smart watch or fitness tracker would be to monitor heartrate and to allow me to set vibration alarms for medication, meals and possibly meetings. Nice to have would include sleep tracking, email and text previews, and I would prefer no built in GPS.