I use an iPhone, but you could do something similar. First off, I use an OtterBox all the time, with the belt clip. On the bike, I took my wife's OtterBox belt clip, since she wasn't using it, and drilled a hole through it (a smaller hole in the clip itself, then a larger one through the flat back of the holder so that I could get a screwdriver through the back) so that I could screw it to a handlebar mount I had laying around.
Just one way of doing it.