Yep! You can accept and make calls with an Apple Watch, even with the non-cellular version, as long as your phone is in bluetooth range. It even works without being connected to headphones, although I can't recommend that for long calls.

With the cellular version and the appropriate mobile contract you're not bound to the iPhone bluetooth range anymore.

Oh okay Well you just made it easier for me. I’ll definitely get an apple watch to stay connected with calls whenever I lock my phone in kitchensafe

Thanks