Hibernate MacBook on 10-ish % power instead of 0/1% when running on battery?

http://www.jinx.de/SmartSleep.html will let you control it via GUI. The app is $6 on his website or $4 on the Mac App Store.

(Note: I have no idea how this app ever got approved for the Mac App Store, but it appears that Apple is stone-walling the developer on approving a Lion-compatible update. This seems to be Apple's passive-aggressive way of getting apps out of the Mac App Store after they were approved: they don't want to upset people by yanking the app, so they just won't approve an update and eventually it either breaks and the developer pulls the app because they are getting so many support requests, or people just stop buying it. When the sandboxing rules hit in November, we may see apps start disappearing from the Mac App Store. All of which is to say that if I was going to buy this app, I'd buy it through his website even though it's $2 more. There's a demo available, although the "request a trial" button didn't work for me, I assume it's a temporary glitch that the developer can fix. It also appears that Mac App Store customers can download the version from his website and use that, so if those $2 are really important to you, I guess you could try that.)

If you'd rather spend time than money, http://tidbits.com/article/9115 has a script that might help.

If you purchase or try the demo version of TinkerTool System (and make sure that it is "system", TinkerTool alone won't do it), there is a setting to enable or disable "Safe Sleep," which automatically hibernates the laptop every time it enters sleep. To access this setting, go to TinkerTool System > Mobile Settings > Safe Sleep.