If you are putting one in your house, make sure it is screwed into/mounted into solid wood (2 by 4) behind the wall. If it's not properly mounted, it could break loose when someone leans their full weight on it. This could result in a fall and injuries.
I don't know how one would install one in a MH or trailer. You'd have to make sure you have something solid to screw into.
You might want to get a hand held shower head and a shower bench to sit on, if you are unsteady on your feet in the shower. It would still be a good idea to have grab bars to hold on to.