Another who absolutely thinks your idea is top notch! I used to do Search and Rescue, and I'll tell you that "filing a flight plan" in as many places as possible is a fabulous idea. I wish more people would do that!! It gives a starting point for search teams and trailing dogs if you do get lost.
If I'm hiking solo (well, I never go without my dog, but as he cannot dial 911, it's solo enough), I leave a description of the route I expect to take, the time I left and the time I expect to be back, on the driver's seat of my car. I also leave the same set of info at home.
When I leave from the house, I also leave a detailed description of where I am going and what time I expect to be home (this is important so people know when to start worrying - I always leave a buffer of about an hour or two - depending on the complexity of the hike/ride/run).
I know we don't expect to get lost or get hurt, but neither did any of the people I have searched for. And it never hurts to carry a little extra food, water and even a solar blanket (they come wrapped up and are about the size of a thick wallet) just in case you are forced to spend the night in the dark.
*steps off soap box*
Christine
Life is not measured by the number of breaths we take, but by the moments that take our breath away.
Cycle! It's Good for the Wattle; it's good for the can!