Check out the promo video that I created for my business affiliate, IK Multimedia:
They've got a cool external microphone which you can plug into your Android device (make sure your Android device can accept an external microphone via the headphone port) or your iPhone. The demo was recorded on on my Motorola Defy (Android 4.1.1, with CyanoGen Mod 10.0) with an iRig Mic Cast microphone plugged in. It's a cool little mike that records better than the built in microphone and it looks pretty cool too. :).
For more information on the iRig Mic Cast microphone, you can check it out here: