TAXI.com

or any other recording device by your side 24/7 .... Any idea I have for a song goes into my iPhone, no matter where I am. When I'm ready to work on something new I go to my iPhone, listen to an idea and start writing .... It's WAY better then sitting down and waiting for something to come to me while I noodle on the guitar.

just to add...anywhere you come up with an idea with your iphone, Apple will know where you were when you came up with the idea.