Build in a timer?

Hi! I am looking to build in a nice timer to a Glide app. The use case is:

  • individual is taking a corona spit test
  • once the mixture is dropped onto a ‘cassette’, the user needs to wait 15 mins (not before) for the strip colors to appear, and not more than 20 mins (otherwise it fades)
  • so it would be great to embed a component (webview?) that has a nice custom timer for 15 mins with a noise.

I did a brief test with Big Timer | Fullscreen countdown timer to see if it would even work (and it does, even if you turn the phone off).

Has anyone done anything like this? Thanks! M