Glad to hear it!
The simplest solution (though not the best) is just to add the command to /etc/rc.local and background it with an ampersand (&) at the end. If you want to implement a proper forking process you can do something like
this and omit the ugly forced backgrounding.
Haven't messed with the netduino, though I do have an Arduino Uno sitting on my desk that I haven't had a chance to write docs for yet. I'd imagine you can hook it up similarly to the
BeagleBone Black. You'd just have to figure out the correct pins on the netduino side. Googling for 'netduino ttl serial' will probably get you some results.