Runtastic Six Pack
Free (in-app purchases) Runtastic GmbH runtastic.com
From the iOS app you can select from a range of ab exercises across three difficulty levels and a series of pre-defined workouts are available as in-app purchases. You can also create a custom workout plan and define the number of sets and repetitions. Routines are initiated and timed from the Watch, which displays animated demos of exercises, logs progress and manages your rest periods.