Most support AAC though, which is in the Bluetooth standard somewhere. At least when connected to the iPhone that sounds as good as apt-X, even on really good headphones.

I've run into this issue a few times with headphones that do: - apt-X only - apt-X + AAC - AAC only - neither

and as long as it supports AAC it sounds good with Apple devices. Sadly, manufacturers don't really put it on the label so it's hard to know.