The Lynwo BT01 is a cheap smartwatch that still packs plenty of features. The device, which retails for under US$20, is IP68 certified and supports GPS route tracking. There is even a heart rate monitor to complement the smartwatch's 1.3-inch IPS touchscreen display.
https://www.notebookcheck.net/Lynwo-BT01-A-sub-US-20-smartwatch-with-IP68-certification-a-heart-rate-monitor-and-onboard-GPS.478957.0.html