You could call the Bokeh app the evolution of the diary. Michael Zhang, the founder of the photography site PetaPixel, created the app to make it easier for folks to create a record of their lives. The app is incredibly easy to use. Simply open it up and add either a photo (with or without text) or text about what you're currently doing or thinking. The app records the data and puts it online on a blog that you can make either public or private.
The Bokeh app makes it ridiculously easy to live-blog your day as you can update it anytime simply by turning on your phone. Additionally, the site itself is a great way to see where you were in the past as it allows you to access any of your old posts via a clickable calendar. The Bokeh app is available for iOS now and an Android version is currently in development.