Jarrod Whaley has a great workflow for entering Day One Entries using a CLI and Alfred 2:

In a previous post, I outlined my method for rapidly firing off a DayOne entry using Drafts for iOS. I’d like to follow up with a couple of methods I’ve devised for doing what amounts to the same thing when I’m sitting at my Mac. Sure, it’s not that big a deal to open up DayOne, wait for the app to load, enter a passcode, hit the ‘new entry’ button…but all of that takes a little longer than I’d like it to when I just want to jot something down quickly and then get right back into what I was doing. So I’ve come up with two solutions to this problem: one is a very simple workflow for Alfred 2, and the other is an OS X System Service.

This is right up my alley. Any time I can integrate Alfred, I do it in a heartbeat. Make sure to check out the mentioned previous post to see how it can be done remotely using Drafts on iOS.