Controlling LEDs from the Shell

I wish the device would indicate via flashing LED that I had a message or alert waiting. I didn't find a way to do it via the regular interface, but from the command line I can at least control the led via the sysfs mounted on /sys

The list of LEDs are:

root@castle:/sys/class/leds# ls -F
core_navi_center/  core_navi_left/    core_navi_right/   kbd_bl_led_center/ kbd_bl_led_left/   kbd_bl_led_right/

the core_navi_left is the left-bottom white led in the "gesture" area.

root@castle:/sys/class/leds/core_navi_left# ls -F
brightness  device@     power/      subsystem@  uevent

with the device sleeping and no panel leds on:

root@castle:/sys/class/leds/core_navi_left# cat brightness 
0

to make one of the LEDs light up

root@castle:/sys/class/leds/core_navi_left# echo 50 > brightness 

that set the intensity at about 50%. The only numeric values that made any visible change were in the range of 0-100. Setting it back to zero turned off the LED:

root@castle:/sys/class/leds/core_navi_left# echo 0 > brightness 

So if I want it bad enough, and nobody finds an easier way to do it in the app framework, I could probably write a shell script or some awful hack to manually twiddle the LEDs