What should I do about this?

I am going to the Calgary Stampede. I currently have an iPhone 4, and I don't want to break it there on all the rides; which is all i do there. I cannot leave it at home incase my mother needs to reach me, and I am not going to go home that night as I am going to my friend's house so i can guaranty I will need it. i can't throw it in my bag because it will break in there, and it will fall out of my pockets. I was thinking of sticking it in the waste band of my pants, inside my underwear on the left hipish area. I'm rather skinny so I don't have fat to hold it down, will this work? Or do you have an idea of what to do? I like going on the exciting rides, like the ones that go upside down and stuff.