The first issue would pertain to someone at a concert or other noisy event who cannot hear the person on the other end of a call. The patent filing shows a speech-to-text solution for this, which would essentially transcribe what the person is saying and show the text on-screen for you to read. This would also be a very effective solution for a deaf person who wants to use an iPhone. The patent shows that the iPhone would prompt the user to turn on this feature based on ambient noise detected through the device microphone.
The second issue would be aimed at someone in a meeting or library who needs to communicate over the phone without using text messaging. The text-to-speech solution shown for this would allow the user to initiate a pre-recorded message for the person calling, or allow the user to input text which would be "read" to the person on the other end of the line. It probably wouldn't be a surprise to hear Alex from the Mac OS speaking the text.
The last patent filing shows a new call hold system for the iPhone which would allow users to place calls on hold and have a recorded message play for the caller. It certainly sounds good, but hearing some on-hold muzak when calling Mom on Sunday may get a bit annoying.
source: Patently Apple