If you move forward with this, one option is to setup your car as a repeater. You can park your car at the trailhead and turn on the repeater in your car. Then the idea is to hopefully hit your car from your handheld, then your car can hit a repeater. In addition to the additional radio in the car that supports Cross-Band repeating, you will need to add a battery or two to your car, and a fresh one in the trunk.
Like others have all pointed out, the handheld frequencies are all generally line of site. This could mean that in a real emergency, you may need to climb to the top of the nearest peak to actually have line of site to anyone. Then once on the top of the peak you may find that your cell phone works as well!
Amateur radios work great in the backcountry in communicating with your own party in a different campsite or at a base camp while you continue on up to a summit.
The SPOTs as you have already researched works pretty well. I especially like the non-911 "Help" button, which just sends a predefined message to someone. I think this is a great feature, as you may need someone you know to start hiking up to you to help you out, but may not need a full Search and Rescue.