EverSave

EverSave is a recommendable application for Mac to automatically activate the 'Save' feature for any application you want, after a certain period of time or when an application is in the foreground.

Add the applications manually from the preferences panel or let the program include them automatically. Don't forget to add those which have to be ignored as well (EverSave already includes Safari, Finder, and iTunes in that list).

Define your preferred saving interval and method to be used by EverSave. One of them automatically launches the keyboard shortcut directed to the application's saving function; the other one is internal, but doesn't have as much compatibility.