Strong.app - Strenght training logger.
WorkoutSesh - Free workout routines with interval timer
wger - FLOSS workout, fitness and weight manager/tracker written with Django
ThinkThinly - Motivational text messages sent at workout times.
Bolt - Workout Tracker - Track your progress in the gym and discover new workouts with the most intuitive workout tracker for weight lifting on the App Store.
Tabata Timer - Tabata Timer is a mobile application that helps you perform high-intensity workouts.