Moji gps watch, a dangerous device

Baught the moji wach it didnt work and battery swelled up so i trashed it baught the moji active x2 had trubble setting it up the app didnt work at all so i paid for a differant app wich alowd only the gps location function but this was after about 3 months of strugeling, kids finaly had them on n my 6 year old and 4 year old got blue brueses on there wrists after a week.