Day One is an elegantly designed journaling application that runs on iOS and on OS X. It’s cloud integrated so that everything stays in sync and is accessible from anywhere. I use it and it’s an excellent tool. I highly recommend it.
Day One is made by Bloom Built, LLC and here’s their description.
Day One is a journaling app for the iPhone, iPad and Mac. Record life as you live it. From once-in-a-lifetime events to everyday moments, Day One’s elegant interface makes journaling your life a simple pleasure.