Layout rearrangement and a few UI / UX / Interaction design recommendations to improve the example overall. 

• Top menu underline and colour of the buttons
  -> to make clear which tab is selected
• Rearrangement of Found Devices section with text size and padding change for bluetooth address
  -> to improve reading
• Found Devices extra suggestion: a small copy to clipboard icon for the bluetooth address
  -> to support developers on checking and testing
• Notification Message box repositioning, resizing, colour change, style
  -> to separate from top menu and improve reading contrast
• Notification Messages order including an initial message
  -> to make the steps clear
• Start button colour change
  -> to emphasise hierarchy and button function
• Layout of instruction text on "Measure" tab
  -> to make text clear in order of steps and improve layout visual and reading experience
• Layout of measure panel and time count box
  -> to improve layout visual and reading experience
• Layout of "Stats" page
  -> to improve layout visual and reading experience
• Measure panel extra suggestion: heart beat animation if possible to implement
  -> run Figma prototype and click on Start at the "Measure" page to see animation