I have a house containing guns and sharps, guns well secured but ammo not, and had two mobile children over for Xmas who might be in danger from the sharps (bayonet collection, mostly), so I made the upstairs off-limits, and put one of these handy-dandy alarms in place at the head of the stairs (sensor unit), with the receiver unit/alarm box down in the living area.
It worked well. I have been using a model of these out on my property perimeter to secure the M-35A2 bug-out truck, and that first one just turned up it's toes after 2.5 years service in the rain, freezes and baking sun in summer.
Two years-plus service is okay for the price I get these for. Note: at "Hardly Freight", they are half of the Shack's price, and sometimes on sale for less. If you are going to use multiple ones, you have to make sure to buy them on different channels, but I noticed that the new ones don't list the channel, hmmmmmm. My old one was marked "Channel 5".
Their function is to protect everything in front of the motion-detecting sender. It has very good detection sensitivity, it alarms on my cat when the Orange Terror struts the hallway between his various napping positions and his scratch box in the upstairs laundry room. Outdoors, it will alarm on a man working seventy feet away in the neighbor's yard, then send the signal to the box inside my house 105 feet from the sensor, through a cedar-board fence and a box hedge. The alarm is a loud tone which can be subdued to a less-loud tone. It will get your attention, and my old ears can hear the soft tone a half-house away while inside.
Seems to me that this would make a useful travel system. In a sedan, you could set it up on the package deck facing forward, and if anyone got into your car, it would sound off in your room, assuming you could park within 400 feet line-of-sight distance of your room.
Good stuff, but not stealthy. If you have it set on loud, and the thief it detects is nearby, the thief will hear the warning. I suppose a savvy e-builder could mod it to have a silent alarm somehow, but that's a challenge, as it has a sealed chassis which would not then be sealed anymore.
For SHTF preps, this alarm uses both AAA and AA cells, which should be in your kit in the rechargeable variety, right next to your solar charger, right?