I have been wondering the same exact thing?
When I look at Apple iOS 8 Messages page they just say Messages got so much better with audio and video recording possible. They don't say anything anywhere if this is an iMessage feature only, meaning you and the receiver need be using an iDevice and iMessage. I also can't see any technical reason why it should be an iMessage feature only. Why would it not be possible to send audio and video as MMS?
But when I am using Messages App I only see the microphone when messaging a contact that is also using iMessage. But even that seems very buggi to me.
I am using a iPhone 5, public iOS8 and iMessage. My wife is running iOS 7.1.2 on an iPhone 4S and we are both using iMessage. The messages app gives me the audio microphone option. But when I record something and send it off to my wife heres what happens: the audio recording turns blue as in imessage format, that briefly I get the red exclamation mark and a notification saying send failure, then the second after the audio recording - still on my screen - turns green, it gets send, and then it turns blue again.
What's up with the blue and green changing light? Is anyone else seeing this weird behaviour or is it working perfectly for you guys?
Do you know if it is supposed to work with MMS messaging or only iMessage?