What’s the best fitness tracker for kids? We think the Garmin Vivofit Jr 3 (buy now) is the best fitness tracker for kids overall. Other kids’ fitness tracker recommendationsBest fitness tracker for younger kids The Fitbit Ace 3 (buy now) wraps up Fitbit’s staple tracking features in a playful design that both parents and children will definitely have plenty of time for. The best fitness trackers for kids you can buy today:1. How to choose the best kids’ fitness trackerWhen you’re picking out a fitness tracker for kids, the first things to think about are design and toughness.