Now then, it's kinda known that the best watch in the world is a Casio F-91w (god-tier), fact, but surely this is screaming out to be a close hackable contender https://www.casio.com/uk/watches/casio/product.F-B100W-1A/ Step tracker, Bluetooth sync and no charging cable? Oh hell yes CR2016 and say no more. Oh and hackable you bet. At that price point, this seems like a good winter exploration project with the kids here.