At a Glance
The screen backlight on most Android phones uses a ton of battery power. Though you can globally tweak the timeout that turns off the backlight, in some circumstances you just don't want the backlight to go out. Maybe you're using an app while driving, and don't want to take your hands off the wheel, for instance, or maybe the app you're using loses data or switches off altogether if the phone locks up its screen while the app is running. For those times, there's KeepScreen.
The KeepScreen tool lists all of the installed apps on your phone; then, with a tap, you can indicate which apps the screen shouldn't cut out on when they're running. KeepScreen runs as a service, which means it doesn't take up system resources as much as a full-blown app does. You can start or stop the service from within the app, or you can end it with an app like TasKiller (also by the same developer). Optionally, KeepScreen will pop up an alert message in the notification area when a program has invoked its services. You can also set a "minimum luminosity" option, which reduces the backlight brightness but keeps the screen lit.
With KeepScreen you can turn down the screen backlight timer to its lowest setting--30 seconds--and preserve battery life, while retaining full functionality and control over the apps you need to use. Sounds good to me.