I was surprised last week to be able to take an incoming call to my iPhone 5 — from my iPad 3. Call was forwarded!
My understanding is that the same call forwarding will now also happen between the iPhone and MAC desktops/laptops.
It does so long as your devices share the same Apple ID and are on the same WIFI network. Worked for me yesterday. My iPhone was in the bedroom on the charger and I answered two calls, one on my MacBook Air, and one on my iPad Air. Cool.