My annual hunting trip is to CO for elk. Our hunting cabin is at 9200 feet, and it's all up from there. Coming from 156 feet, it get's more difficult every year as I get older.
For field maintenance I carry an Otis cable kit and a small torx wrenches (l-shaped like allen wrenches) which were provided with both my scope and rings. I also carry a Lens Pen and small cloth.
As far as safety, I carry 2-3 liters of water in a backpack bladder, paracord, a Gerber multi-tool, small first aid kit, a loud whistle, emergency blanket, compass, headlamp with extra batteries, nitrile gloves, waterproof matches, flint and lint for firestarting, several aspirin, 10 rounds of ammo in addition to the 3 in the rifle, and an extra pack of smokes.