wool has the amazing ability to "felt"
I will try and explain, go to your local craft store and in an apropriate color get some wool batting, or yarn and seperate it into fine fibers. , then lay the torn spot over a block of styrofoam, then lay a pile of the wool fibers over the tear (you can use a form like a cookie cuter if you want to create a patch with some shape) then you can use a pin (they make special ones but any blunt pin or needle will work) to push the fibers through the torn material, when you have a mass of fibers pushed through and on both sides of the torn jacket, put an iron on heavy steam and iron both sides of the patch, this will "felt" the wool together into one solid piece, then you just have to pull out any stragler pieces and off you go with a fixed jacket
you can also use this method to sturdy up the elbows or any high wear part of your wool clothing before it gets worn out. I will try and find a tutorial online and post a link to it.