How to Send Audio and Video iMessages on Your iPhone
When you tap the dictation button on the Messages keyboard, you dictate your message on the iPhone but it’s sent as a written text message. With iOS 8, you can send recorded voice and video messages to your iMessage-enabled contacts with the following steps:
Touch and hold the Voice Message button (the microphone next to the text field) and begin speaking.
If you want to cancel your message before sending it, lift your finger, and then tap the X to the left.
To send an instant video, touch and hold the Camera button to the left of the text field. Tap the Record button (the red circle) and begin recording. Tap the Stop button (the red square) to end recording.
(Optional.) Tap the Play button to hear or see what you recorded before sending it.
Tap or swipe up to the Send button (the upward pointing arrow) to deliver your message.
The recording appears as an outgoing message in the conversation.
If you receive an audio message, raise your iPhone to your ear or tap the Play button to listen to it.
Choose to delete your instant recordings after two minutes or never in the Messages Settings.