Simple Interval Timer is a free, user-friendly HIIT timer that aims to help users focus on their workout instead of wasting time on working out how to start the timer. The app is designed to assist with a variety of activities such as boxing, circuit training, HIIT training, Tabata, and weightlifting. With a simple interface, users can easily customize the number of sets, length of sets, and rest length.

One of the best features of this app is the round end sounds that alert the user when each set is complete. The app also requires minimal permissions, only requiring internet access to support a small banner ad at the bottom of the screen. Overall, Simple Interval Timer is an excellent tool for those looking for a straightforward and efficient way to manage their interval training.