I am not the original author. I found this plugin and forked it because I wanted it to control the ThinkLight on my ThinkPads, which requires you to write "on" or "off", not "1" or "0", to /proc/acpi/ibm/light. I sent a patch to the original author but never received a response.
Below is the original README text.
Led-notification, a Pidgin plugin
Led-notification can control leds found on some laptops, or anything else that is controlled by writing '1' or '0' to a file.
Simo Mattila <email@example.com>
* Initial version
* Add XSet support <firstname.lastname@example.org>
A pidgin plugin to use an LED to notify the user of new IM messages.