Which fitness tracker to choose for a grandmother?

Question

Mobile devices

There is a task to monitor the heart rate during the day and then the collected statistics

• Monitoring every 15 - 20 minutes, etc. and in a dream
  
• Determining the heart rate value on demand
  
• Monitoring of general activity during the day
  
• Bright and legible display
  

Optional:

• Sleep monitoring
  
• Long-term low activity alert
  

Can you tell me a device that meets these requirements? Thank you.

Answer 1

Mio Slice

Answer 2

Microsoft Band
from the budget - erase it yourself, Polar all sorts, etc., Fitbit seems to be able to too