rob,
my first take at this is not from the automation side, but from the safety side. The only wood fired boilers I'm aware of that are rated for indoor usage are the Tarm, and AHS boilers, which are both wood gasification boilers, and as such, should not have issues with chimney fires as they are designed to gassify and burn the smoke, preventing the formation of creosote and the main cause of flue fires. Now if your friend installed an OUTDOOR wood boiler in his home, I would be very worried about the liability of helping him automate something inherently designed without a lot of controls and to be OUTSIDE! Most outdoor wood boilers are little more than tanks of water with a fire chamber at the middle, and as the smoke from wood needs +2000F to burn, the cold surface of the water backed steel chamber makes them inherently smoky. A little more info please?