I use an Otter Box Defender phone case for my Droid Incredible 2 and my wife has one for her iPhone 4 and they are bulletproof if you decide to go that route. They're also waterproof.Good for navigation:
Another option would be a handlebar mount for your android with gmaps and mytracks apps installed. This setup works pretty good if you don't mind risking damage to your phone. They now make waterproof/shock resistant android phones, the Samsung Galaxy Xcover is one of them.
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They now make waterproof/shock resistant android phones, the Samsung Galaxy Xcover is one of them.