Originally Posted by
HDQDD
Actually they can. You can also get SMS (and iMessage) on OS X Yosemite. I use it all the time. However, I believe it's somehow linked to my iPhone, and I suspect it wouldn't work if I didn't have phone service.
Yeah, the feature was introduced on iOS 8. Your phone communicates via the local wifi network with other devices signed into the same Apple account on the local network. It's the same way I can make regular phone calls on my iPad - it goes over wifi to my phone.