It's called Day One and is basically a photo journal on your iPhone or iPad.
I've been using it for around 3 years now but it really came into its own through my pregnancy and with the arrival of Baby D. I ensure I take at least one photo a day (more often than not of Baby D) add tags and a short description and that's it. It records where the photo was taken and at what time plus what the weather was like and sorts them into chronological order.
|photo view option|
It costs £3.99 through the App Store and to me is worth every penny!
Let me know if you have it or get it and what you think of it.