x100 is a free iPhone app developed by Astroshock LLC under the Lifestyle category, specifically catering to Health & Fitness enthusiasts. This app simplifies workout sessions by keeping track of your reps, allowing you to focus on your exercises while it handles the counting.

With x100, you can set the number of reps and begin a 5-second countdown before commencing your workout. The app's algorithm focuses on the initial reps to identify your movement pattern. It allows breaks during sets and automatically resumes counting when you continue. Additionally, you can restart sets with a simple gesture, manage presets, track statistics, and customize sound settings.

However, x100 is best suited for simple repetitive movements and requires stable phone positioning for accurate counting. It offers a seamless experience with features like Sign In with Apple and data transfer capabilities for a personalized workout tracking experience.