There are some tools which allow to get information from your computer without using the monitor:
bl : Blink Keyboard LEDs
blinkd : "Blinks keyboard LEDs for an answering machine or fax machine. Blinkd is a client/server pair, that lets the keyboard LEDs blink, indicating things like the number of incoming voice calls in the voice box or incoming faxes in the spool."
mailleds : Shows new mails with the keyboard LEDs, mailleds is a quiet, unobtrusive way to signify that you have new mail: a user daemon to blink LEDs when there is new mail.
tleds : Blinks keyboard LEDs indicating TX and RX network packets. They blink Scroll-Lock LED when a network packet leaves the machine, and Num-Lock LED when one is received.