In my search for a smart watch that has basic functionality outside its native app, I've come across this watch from Ebay, "Smart Watch Touch Bluetooth Heart Rate Fitness Sport Waterproof For Android iOS". I saw that it was inexpensive, had a IP68 water proof rating, and works without app dependency.
The native app for this smartwatch is called Fitpro.
Unfortunately, IP68 waterproof rating is false. This wasn't fully submerged in water but made inoperable from a simple shower. Requested a refund and I was offered a full refund within 24 hours. Looking for a smartwatch once again. Updates coming.
