Timer+ (free, paid options)

If you've ever used a kitchen timer which can time more than one event simultaneously, you know what Timer+ does.

iOS has a built-in countdown timer, but if you need to time more than one event concurrently, this is a fine solution.

I started using this while digitizing hundreds of videotapes, to alert me that I should check on the progress of two or three concurrent transfers. You can name alarms, and the sounds can be individually set. You can pause and cancel any running timers, and see all the timers at once.

The free version is adequate for me. Paid features add sounds ($0.99) and eliminate the advertising banner ($1.99).