I’ve put together a few ideas on retreat security that I haven’t seen on your great site. I may have missed them but I think they would bear repeating. I presently live near Philadelphia, Pennsylvania, but will soon be moving to my 280 acre ranch in central Nevada. What got me to write this was a realization during my semiannual chore of servicing the emergency generator. Changing out the gas (It is also set up to run it on propane) changing the oil, and testing the circuitry, I realized that what I thought was a good setup was actually lacking. I have always made the preparedness of our home priority. If a storm knocks out the power, I go start the generator and switch the control box. My “Ah-ha” moment came with the realization that if the power were ever cut intentionally, all security would be off until after I’d expose myself to go start the generator. Needless to say corrective action projects (remote start, auto control panels, and UPS  battery backup for the security system) are now underway.
Education has been mentioned but I realized that I hadn’t seen much about basic electronics. Learning how to make small circuit boards is really rather simple, and allows you to make a lot of toys (equipment) for the homestead. A simple IR  detection circuit to let you know if someone is coming in under cover of night. A display can show which sensors are being activated. This way you have a choice, whether or not to let someone know you are alert to their presence. Pressure [sensing] pads you can make yourself to show if someone is standing behind that large boulder, by the barn, or shed. [JWR Adds: Commercially-made pressure sensing pads are far more reliable weather-resistant. Used ones are sometimes sold as surplus by alarm companies.] How about a simple circuit that is connected to motion/heat sensors in the house that light an LED  array that not only shows someone is in your house but on which floor or in which room. There are electronics parts vendor sites like Jameco  and DigiKey  and web sites like Instructables.com , Makezine  and similar hobby and hacking sites that show all sorts of projects and skills.
When I get my next batch of wire I am setting small speakers to exploit a bit of human nature by creating a brief sound to get intruders to look in a particular direction and then two seconds later turn on concealed 500 Watt floodlights for a blinding effect. These floodlights will be good for general use as well. I mentioned pressure pads for detection earlier. One of the ideas at the ranch was to place large cover objects at strategic points to funnel a potential intruder to a place he could hide and I could remote view the opposition at the same time. Mini cams and mikes and alarm pressure pads will give you a heads up.
Since my ranch a long way from law enforcement protection, a remote defense is also installed. Behind two of the boulders I had moved with the rented dozer, I placed a small outcropping of rock in the ground so as to leave nothing to hide behind but left a cavity in front to set plastic bagged SKS  rifles (sans stocks) [in mounting frames with solenoid-actuated triggers and] cameras at the scope (which by the way is a great way to aim around corners) and the aiming is done by remote control units from the hobby shop (or eBay). Solar power and small batteries keep things operational. (I am sure the liabilities and legalities will be questioned, so let’s say the property is set up for installation after TSHTF ). Safety is important so the units are double switched, one to turn on the power and the other to control and fire. The third unit is similar but I made a small bracket on the tree behind the third cover position, laid in my controls, made a cloth skirt at the base to allow movement and then used the foam insulation in a spray can  and made a foam cover to look like a branch and spray painted with a couple of colors . This made it so invisible that a visiting friend couldn’t detect it even after I told him where it was. The cost for cameras, microphones, controllers, and sensors is really small–from under $2 for sensors to perhaps $25 for the others. What you pay big bucks for is the labor and knowledge. But you you get that by turning off the television and exercising your brain.
[JWR Adds: Consult your state and local laws on “trap guns” before considering any such installation. Also keep in mind that any semi-auto firearm that is triggered via solenoid might be construed to be a ” machinegun” if there is any way whatsoever that more than one cartridge could be fired by a single press of the remote “trigger”. Also, keep in mind that in the US, Federal law that restricts not only barrel length but also overall length for a firearm. (Rifles and shotguns must have a minimum overall length of 26 inches.) Multiply-redundant safeties should be designed, as a well as a safe backstop for any bullets fired. In my opinion, installation of a remotely-fired gun should only be considered in absolute “worst case” situations. Their use in any lesser situation might very well land your in court, on trial either criminally and/or civilly, in a very bad light that would doubtless be exploited by hostile attorneys.]
Before I leave this topic I would add that on the previous mentioned web sites and YouTube.com and Google video you can learn how to pick locks, scavenge old camera parts, make and run a forge, start fires, throw flame, make thermite, generate smoke and just about anything else you can think of. Its like having a couple hundred mischievous people in your R&D  department.
How about remote cameras? There are gadget sites, military and defense corporations, and especially university sites have many ideas, for free, such as GizMag , DARPA , and MIT . One topic of interest is remote viewing. You can launch a hand held and nearly silent electronic plane and view all points of the ranch in very short amount of time without exposing yourself. It could also be used to find wild game. [This is called “First Person View (FPV) piloting .] Try a web search on “remote FPV flying” and watch a couple of videos. The aforementioned hobby web sites are also a resource on model aircraft information. [JWR Adds: Radio control aircraft servos have numerous uses for folks with creative minds.] Prices range from $300-to-$400 to as much as $1,500 This can be applied to rc cars adding remote microphone and speaker, and rc helicopters as well. It only took a couple of hours to get a real good feel for it,. But I should add that I haven’t yet flown it in high wind.
To set up [for security at] the ranch property I mapped out GPS  way points and used a range finder for all the prominent features. I would also suggest a picture of the property and the surrounding properties from Google maps . At several strategic spots I planted some damaged concrete sewer pipes on end–I had obtained these free for the asking–and made large lids for them with a plastic base and the aforementioned spray can foam to look like the landscape, with a hollow center so you could look out small holes without moving the lid. Inside is water and there are a couple of ammo cans for food, and a small seat and space blanket, iron oxide hand warmers which are also good for emergency in your car and coat pocket or keeping vigil at a remote hide–[a small heat source] can be the difference between bearable, frostbitten, or dead. I’ve requested more of the free concrete pipes be saved so that I can bury them between the house and the barn and run a little shuttle between the two buildings. Why not,? The price is right.
For structure fire suppression and prevention, I’ll just mention these two products as a one-time fire insurance policy: ThemoGel  and Barricade . Perhaps at some point this could also be made a remotely-triggered function. I hope you find some of this useful. – Erik