Some stores value customer relations more than others and will replace items damaged by simple accidents (sometimes the laws are written that they have to as well, but that depends on the country) If you purchased from a store they can at their discretion give you a replacement.
Generally a fitness device esp one that is likely to be knocked a bit should be able to take a small amount of impact. If it was just a step counter then no, impact effect would not be an issue, but a tracker that is designed to be used with weights, cross country runs, triathlons, iron man, boxing, martial arts even tennis where the device may get knocked (from fall or impact of a tennis ball or even a weight bar) should be covered, but that is my opinion although in some countries that is also the opinion of the law as well.
I really depends on the laws and the stores willingness to agree as to what is acceptable damage through use and what is not, a somewhat murky situation. But as I said earlier some stores value customer satisfaction over profiteering (ooh that sounds harsher than it should be, if I think of a better word I'll change it 🙂 )
