This is the little X app that sits in the corner of your screen, looks like the lights on a dn3000, and blinks.
There are a few command line options. See the source for details. Click on the 'A', 'B', and 'C' lights to toggle them. Click on 'D' (heartbeat) to exit. Click on 'Pwr' to turn all lights off.
Also includes xcorner, which turns the display off when you move the mouse pointer to the upper right corner of the screen.
Source tarball:
dnlights.tar.gz