Buy the KIPTUMTEK Smart Watch.

It does more for less and skips the gimmicks the pricier one leans on.

What was compared

KIPTUMTEK Smart Watch for Women Men, Fitness and Sleep Trackers with 1.83" HD Touchscreen,... — $18.99
Fitness Tracker Watch with Heart Rate, Activity Tracker, Pedometer Watch | Step Counter, H... — $19.99
Smart Watch Fitness Tracker with 24/7 Heart Rate, Blood Oxygen Blood Pressure Monitor Slee... — $49.99

1. It actually takes calls, the others don't
KIPTUMTEK has Bluetooth calling built in, so you can answer on your wrist. Neither the LIVIKEY nor the Bestinn advertises this, meaning you're stuck pulling out your phone every time it rings on those two.
2. Bigger, sharper screen than the Bestinn
1.83 inch HD touchscreen versus the Bestinn's 1.58 inch panel. On a wrist-sized display that difference is the gap between comfortably reading a text and squinting at it.
3. Owners are actually happier with this one
KIPTUMTEK holds 4.5 stars while LIVIKEY sits at 4.0 despite way more reviews, meaning a much bigger share of LIVIKEY buyers walked away unsatisfied. More sales doesn't mean better, it just means more people bought it.
4. Cheapest option that does the most
At $18.99 it undercuts the LIVIKEY at $19.99 and crushes the Bestinn's $49.99, while adding calling and a bigger screen neither rival offers. Paying more here buys you less, not more.
5. Yes, Bestinn has BP and oxygen sensors. Ignore that.
Sub-$50 blood pressure and blood oxygen sensors are not medical grade and drift constantly, so that spec sheet advantage rarely holds up in daily use. You're paying nearly 3x more for numbers you can't fully trust anyway.