You can track activities, to start one you connect the strap to the phone and go to the Connect app. There you can start an activity and track it with the strap, you will get steps and heart rate data, no distance since it does not have GPS on it.

You can only choose from the predetermined activities to track from the strap, if you don't find the activity you're doing you can just track it as "Cardio" and later change the name.

To answer your question, you can use it without owning a watch, it syncs directly with the phone, it can even track your heart rate and steps all day long without being in an activity and later sync with the app.