I like the idea
But, can there be an option for setting seconds/minutes/hours? And have the timers linked to go at the same time or to chase each other?
This Timer is Awesome!
I know the guy who wrote it, so I may be a little biased as well.

This utility app provides a straightforward heat-up and cool-down timer. It features a simple interface and visual cues, with screen flashes indicating the end of each interval.
2.1
July 2, 2019
Updated App Icon.
Dual up down timer is designed to help users manage heat-up and cool-down intervals. It's useful for structured workouts or any activity requiring timed segments.
The timer provides visual alerts by flashing the screen black at the end of the heat-up portion and white at the end of the cool-down portion.
Yes, Dual up down timer is available for free, with no in-app purchases or advertisements.
Dual up down timer is compatible with iPhone and iPod devices.
Dual up down timer has an age rating of 4+, making it suitable for a wide range of users.
The app was last updated on July 2, 2019, with version 2.1. It has received updates since its release in 2017.
Users have rated Dual up down timer highly, with an average of 4.8 stars from 4 ratings, indicating positive user sentiment.