Best interval timer for all day?

ritasice21

I want to use an interval timer but not for hiit. I stay at home and have been challenged to walk 1 minute every 15, so I set it to 1 work and 14 rest for x account of setsThe problem I am having is that it stops notifying if I am using my phone or sometimes even clear other notifications. Was wondering if anyone has any ideas other than testing every app in the play store?