DiDO F9 1.8 inch IP67 Waterproof Bluetooth Smartwatch, Support Blood Pressure Monitoring / Sleep Mon worth to buy? Thanks for it if those of you who have purchased DiDO F9 1.8 inch IP67 Waterproof Bluetooth Smartwatch, Support Blood Pressure Monitoring / Sleep Mon could share about what you think of the product. I would love any extra info, as it is quite pricey as $35.60 and I just want to know it is good before paying for it.