RUN interval - Running Timer is a free iPhone app developed by Justin Templar. It falls under the Lifestyle category and specifically the Health & Fitness subcategory. This app allows users to easily set up and record their Interval and Fartlek running sessions. With the flexibility of using time and/or distance as interval targets for their "Hard", "Easy" and "Rest" efforts, runners can create custom interval sessions that suit their individual needs.

The app features a simple yet highly configurable interface on both the phone and Apple Watch, making it convenient for runners to track their sessions. It also offers a Distance Goal option for sessions, detailed post-run summaries, and the ability to share runs to Strava. Additionally, users can record their regular runs with voice-over calling out distance and pace feedback.

With clear visuals, audio prompts, and vibration feedback, RUN interval provides a seamless running experience. The app also includes features such as heart rate zones, indoor mode for treadmill running, and sound mode for discrete audio prompts. It prioritizes user privacy by not sending any data to a server or sharing it with anyone.

Overall, RUN interval - Running Timer is a comprehensive app that caters to runners of all levels. Its user-friendly interface and customizable features make it a valuable tool for tracking and improving running performance.