Cross Game Chat...an exteremely useful feature that wouldn't be very hard to make. Sony already made the "Cross Game Text Chat"...just take that, disable the text, and add microphone support. Simple. Even throw on a little "PS+" icon onto the feature while your at it.
I still don't get why we don't have this yet. We've already got loads of other features (which are PS+ only) which would take A LOT more time and planning then Cross Game Chat...not to mention that this is listed as the number 1 idea in the PS Blog Share.