Having a small deck or mini house in the trees can be very beneficial to be able to see far distances to see people coming miles away before they see you. Obviously a little more camouflaged then these but you get the idea.
Here are some examples of some Observation Deck/Tree house.
There are many type of natural home building methods but one of the most efficient secure and stealth method would have to be the Earth Sheltered home. It can be hidden in a hill side with grass and plants grown all around it so you can barely make out that it is a home. By having the shelter covered with earth on its top back side and sides it creates superior insulation in the winter months and allows cooling in the summer being lower in the ground. You can even dig out a small basement area for storing food stuffs at a constant 40-55 degrees year round.One of the best ways to construct a earth sheltered home would be to use rock masonry for the walls and wood logs with wood post buried in the ground wrapped with a waterproof membrane(polyurethane or any other heavy duty waterproof material) so the wood will not rot over time.
Here are some examples of earth sheltered homes.