Got myself a blink(1) mk2 gadget to play with. It is currently set up to alert me to new emails with different colours for the different accounts. This is done using the Mailbox Alert add-on for Thunderbird and the blink1-tool command line tool. Very good instructions may be found on this wiki.
Update Jan. 2015
Unfortunately, after enabling the blink(1)_mk2 notification in Thunderbird as described above, my entire system started to freeze up when I got email. Not every time, but repeatedly. I don’t have time to sort it out at the moment, so I disabled the Mailbox Alert add-on in Thunderbird for the moment. The problem has thus gone away, but it remains unsolved.
The Mailbox Alert add-on may not be necessary, since I believe Thunderbird has message filters that can be set on the inbox, and which can run a command when new mail arrives. I tried this, but the problem persisted. Therefore, I believe the problem lies with the blink1-tool command line tool.
Does anyone else have similar experiences, or maybe even a solution? I am open to suggestions.