Advancing the Story has an article talking about how to shoot news with the iPhone, or other video capable phone.
One of the more important tips:
3. Know your mic. Figure out where the microphone is located and play around a bit to determine how to record the best sound. Generally, you will need to move in close to the source of the sound or interview. If you’re willing to invest a little cash, you can buy external mic kits for smartphones that will improve the audio quality.
With most people having smartphones, it’s important to remember the device. Know the limitations of the medium.