Recommend a good interval timing app

Hi Folks,

Can anybody recommend a good interval timer app for an iphone?

There are so many options.

I don’t mind paying a small fee, as long as there is a simple interface, and no annoying pop ups.

I just want to set a work interval, a rest interval, and number of sets.

It’s for weighted hangs, so the intervals will be measured in seconds, not minutes.

Beeps would be nice so I don’t have top stare at it all the time.

Thanks.

Bruno