With the NoiseFit Endure, you get an inexpensive smartwatch with not only 20 days of battery life, but also with IP68 certification and a heart rate sensor. The NoiseFit Endure also has a 1.28-inch circular LCD panel, over 100 watch faces from which to choose and nine sports modes for fitness tracking.
https://www.notebookcheck.net/The-NoiseFit-Endure-a-smartwatch-with-20-days-battery-life-IP68-certification-and-a-heart-rate-sensor-is-now-shipping-for-INR-3-999-US-53.465610.0.html