It's occurred to me as to why there isn't a profile called 'battery saver'?
When you set your phone to vibrate, silent, etc...there is an option to save battery.
When set, you can toggle what it can do, but it will run along the lines of turning off GPS, turn off NFC, turn off Wifi, adjust screen brightness, reduce backlight timeout, stop applications refreshing in the background, and whatever else. That way you don't have to go around doing it all manually.