The ability to receive calls on any iDevice is one of those genius abilities that makes Apple devices unique. Just last week I was at work and left my iPhone charging in my office. I was literally half way across the building and way out of Bluetooth range.
My Apple Watch 2 rings and I take a call and talk for 20 minutes! The AW2 communicated seamlessly with my distant iPhone over the building's wifi network! The person at the other end of the line couldn't believe I was talking to him on my Apple Watch! Ditto at home. MacBook Pro or iPad.....I can take calls on any of them! This IS starting to feel like the 21st century after all.