This is the ideal timer app if you need a countdown timer that will countdown multiple timers at the same time.

MultiTimer Plus allows you to run and reuse timers for anything happening in your life.

You can create up to 8 different timers, which can run at the same time, and customize them by name.
You can also choose 8 different alarm sounds.

If MultiTimer Plus is in background, no problem.
When you wake up your device you will see the correct time to the end of your task and, at the desired time, MultiTimer Plus will warn you, even if it is running in background.