You don't know when God will ask for a moment of your time. And that's the point. You could set an alarm, sure, but then you will be anticipating and fitting God into YOUR schedule.
"Give time to God, and God will give time to you."
James 4: 13
Twice a day isn't a lot, granted, but it's a start. You tell the app between what hours you want to be reminded and then the church bell will toll, randomly, twice every day to call you to a moment of prayer.
To think about Him. Or thank Him for what is before you.
When you hear the bell, you pause what you are doing for just a moment. Draw a deep breath and give your attention to the God who blessed you with this day.
Surely there is something you might want to say to Him?