There are plenty of interval timing apps available on the market for free or for less than $3 but if for whatever reason you don't want to use a smartphone on your workouts, you can rely on a small interval timer like the Gymboss MiniMax. Many athletes rely on a Gymboss interval timer for running, interval training, HIIT, cardio, tabata, and more because they're user-friendly, convenient, and compact. The MiniMax can track up to 25 different intervals between two seconds and 99 minutes and save up to 20 programs. It also has a built-in stopwatch and clock functions though most people don't use the stopwatch because the buttons aren't sensitive enough. You can set it to beep, vibrate, or both, so you can avoid annoying other gym goers.