Facebook Home has been out and about for select
Android phones since April 12th, and while the whole Home experience is not likely to ever arrive on iOS due to the restrictions of the OS, Facebook is doing its best to bring as much of Home as it can to iPhone
and iPad. The new iOS app update, which is being pushed today for iPad, iPod touch and iPhone, introduce chat heads, so long as you're in the Facebook app. In other words, those who are scrolling through the Facebook app and get a message, will see a chat head pop up. But, due to iOS' limitations, when you leave the Facebook app those heads will vanish.
Stickers and a refined look for iPad are also on the change list, for those interested. If you don't see it in your local iTunes store, keep refreshing!