Beach Camera via Rakuten offers the Garmin Vivofit Jr. 2 Activity Tracker in Spiderman/Black for $59.99. Coupon code "SPORTS20" cuts it to $47.99. With free shipping, that's the lowest price we could find by $12. It features a 1-year battery life, step and sleep tracking, and chore/behavior management.
Retailers mark up products by hundreds of times their cost — but you don't have to pay the premium.