If you have been following what I've been up to lately you would see that many of my recent projects are based on FuelPHP. Since Fuel is so awesome and allows you to create "packages" that can be dropped into your application, I have created a few that help me quickly piece together apps. The first package I'm "releasing" is called Wrench.
The tool works with the oil command-line tool already included in the framework to swap out the default action with a "Down for Maintenance" message. It will look at the current state of the app and switch it to the opposite when run, but you can also define "start" and "finish" manually if you'd like. You can find the source for the package on Tom's github account.