Modern Macs have pretty good battery life, but there are times when you can't get enough juice to keep working without a power adapter. BatterySqueezer promises to help you extend your battery by throttling process that are running in the background.
The idea is that by reducing the amount of processing power demanded by applications that are not actively being used, it reduces overall CPU load. Reduced CPU load results in lower power usage, which in theory, should extend your battery life.
BatterySqueezer sits in the background ready to throttle programs when they're not being used. Currently it supports four browsers, Firefox, Chrome, Opera and Safari, as well as Reeder, Microsoft Office and iWork.
The throttled apps aren't killed off entirely, but plugins such as Flash, animated adverts and any processes that are demanding are reduced to practically no load. This has another benefit other than extended battery life and that's more free resources, which can be particularly useful on a low-powered Mac.
In anecdotal testing BatterySqueezer throttled Flash from some 30% of CPU load to about 3% with Chrome backgrounded. The result was very jerky Flash animations, but who cares when its in the background. As soon as Chrome was brought to the foreground, it was unthrottled and everything was normal. It also had the benefit of keeping my hot-running Mac cooler with noticeably reduced fan speed when multi-tasking. BatterySqueezer is one of those apps that will have different mileage for different people and setups.
If you're trying to eek out as much out of your battery life as possible or trying to stretch out the resources of a low-power Mac, BatterySqueezer might just be the ticket and is available for US$3.99 from the Mac App Store.