Fitness Trackers Safe to Wear? (São Paulo)

I understand Apple Watches and other fancy jewelry is a no-no from a safety perspective (not to attract petty thieves or worse on the street). What about wrist-worn fitness trackers such as FitBits and Jawbone Up?

I'd love be able to continue tracking my steps while in Brazil. Are they common and cheap enough in Brazil (esp. São Paulo) to not pose a significant risk?