Black Smart Bracelet Fitness Tracker Watch Activity With Heart Rate Sleep Monitor Bluetooth Waterpro worth to buy? Thanks for it if those of you who have purchased Black Smart Bracelet Fitness Tracker Watch Activity With Heart Rate Sleep Monitor Bluetooth Waterpro could share about what you think of the product. I would love any extra info, as it is quite pricey as $15.60 and I just want to know it is good before paying for it.