This app was mentioned in 1 comment, with an average of 5.00 upvotes
I think they mean the apps from Runtastic. I use it most days as well, would recommend it.
Android https://play.google.com/store/apps/details?id=com.runtastic.android.sixpack.lite&hl=en
IOS https://itunes.apple.com/us/app/runtastic-six-pack-abs-workout/id685857245?mt=8