I think this is very interesting and holds a lot of potential. I can see all the tech people loving this.
Undoubtedly a waterproof case will be needed unless apple comes out with a waterproof iPhone-the outdoorsman model.
Maybe this will work better on a iPod where you don't have to worry about incoming calls or texts.
Also the app needs to be able to shut off the auto lock or it needs to be turned off ahead of time.
Last you need a warm finger to unlock the iPhone and open apps. I for one have a heck of a time sliding to unlock when I'm in the woods and it's cold out, the iPhone just doesn't unlock with out body heat in the finger tip.
My best wishes because it's a great concept!