i think there is no app for this, but it is possible to do it with tasker.
there is a plugin for tasker which can can use root-rights, or start scripts with root rights. so in you know the right command to turn the backlight on and off you can do it with tasker in a script.
the command to turn off the lights:
echo 0 > sys/class/leds/keyboard-back
and to turn on
echo 255 > sys/class/leds/keyboard-back