FaceTime's been a Wi-Fi only affair for as long as the video calling solution has existed — it didn't even work over speedy LTE — but starting in iOS 6, the restrictions have been lifted. We don't know which networks qualify, though. Will it work over LTE? HSPA+? 3G, perhaps? Apple's not saying right now. What's more, Apple is unifying your phone number and Apple ID such that if you make a FaceTime call or send an iMessage to a person, they'll be able to call, message, or email you back by normal means, and you'll be able to answer calls to your phone number that's linked to FaceTime using any supported device, like your iPad or Mac. We'd have to test it to be sure, but it sounds like Apple's hoping for a seamless experience where people call and message one another as usual, but if you've got FaceTime on tap, it'll simply be that much easier for you to pick up the "phone" as needed.