The KIE OS is a free Android app created by Kieslect os. It's designed to enhance the user experience of the Kieslect ks smartwatch, offering an array of features that sync with the smartwatch.

One of the main features is its ability to relay incoming calls and SMS/MMS messages from your phone to the smartwatch. You can answer calls and read messages straight from your wrist. If you're too busy to take a call, you can reject it and send a quick, pre-set text message. But remember, the app needs "SMS and Call Log Permissions" to perform these tasks.

Another useful feature is its health and fitness tracking. The app records heart rate data and sports metrics like step count, stride frequency, and distance. It presents this data visually in line graphs and histograms for easy understanding. Plus, you can set reminders and alarms on your smartwatch using the app.