Although Apple's laptops offer pretty decent battery life, it's not always enough. Getting the most out of your battery often means making a number of sacrifices like turning off Wi-Fi and lowering your display's brightness. While you can't get something for nothing, BatterySqueezer can extract a little more battery life by automatically throttling applications in the background so they don't cause excess drain while not in use.
BatterySqueezer runs in your menubar and defaults to just throttling your web browser when its in the background. It can also throttle other hungry apps like Microsoft Office, iWork, the Mac App Store and (apparently) Preview. There's a little slider in the preferences (see image above) that lets you determine how responsive background apps are when you return to them, and this is where you realise what you're giving up. When apps are running freely in the background it's so that you can go right back into them without any delay. This has a drain on your battery, however, so BatterySqueezer essentially trades that responsiveness for reduced battery costs.
That's basically all there is to it. You just enter your settings and let BatterySqueezer run. It'll take care of the rest. The full app will cost you $2.99, but there is a free version as well. We're not sure what its limitations are, but reviewers seem to believe it doesn't actually do anything (so you may want to avoid it).
BatterySqueezer ($2.99) [Mac App Store]