There are a lot of smartwatches in the world, and most are differentiated by their features, like sleep tracking and UV sensors. There’s also just the straight-up cheap options. The "U8 Smartwatch with Bluetooth Answer and Dial the Phone Passometer Altitude Meter Burglar Alarm Functions" is a cheap option. It usually retails for $17.56, but it’s now available for $7.79 on Gearbest. Dat’s real cheap.
The site also has other smartwatches listed for $8.47 and $9.28. Look at all these cheap options! Here's what I know about the U8: it only works on Android, can make phone calls, and it doesn't come with a manual when it ships. It’s also not waterproof but does have a touchscreen. (The below video says waterproof, but Gearbest's Q&A says it's not, so I'm not sure what's going on there.) It’s $7. It apparently functions. Here it is in action: