I use an app called "Acar" which recently was bought out by Fuelly. The app costs a few bucks, but worth every penny. You can enter in maintenance, fill-ups, and recently they added the ability to upload pictures with each log entry. It also has reminders, which you can set to whichever interval you prefer. I normally don't forget oil changes, but it's handy for things like remembering to check air pressure periodically, rotating tires, air filter, those sorts of things. If you record fuel fills, the reminder is spot on and and lets you know ahead of time when you need service-- or you can take a quick glance and see when the next services are due.