How close do the watch and phone have to be for full functionality of the watch?

[iMore Question]

Can workout at the gym and just wear the Apple Watch and leave my iPhone in my locker and still listen to music and receive texts, calls etc? Or , if I go for a jog, do I have to strap the phone to my arm? In other words I am stuck with having to keep the phone close to use all the functions of the watch?

 

[Highrisedrifter]

It's within standard Bluetooth range, I believe.