We did one, mainly to get straight in our heads what we did and didn't want to do, really it was as a communication aid between ourselves. But I did discuss it with my homebirth midwife too.
I had a separate section headed 'in case of transfer to hospital' that covered things that were specific to this. I put the whole thing in my notes (home and hospital parts). I did end up in hospital and the hospital midwife was very careful about reading it all, and trying to follow it all as much as was practicable, even the more 'home' bits of it.