Confess as someone who spends way to much time on the sports field that I got an otterbox defender for my iPhone 4
Worst thing that's happened was my Golden deciding it was chewable. iPhone lived, otterbox died and golden got a real stern talking to.
A friend of mine runs a land rover / range rover specialty repair shop. Based on his experience, they are capable of stopping anywhere, anytime, at any cost.
I don't know about the brakes, only their unreliability.