[this is a cross post to the safes & home security forum - same need, but possibly different audiences]

I'm not sure if this is the right sub forum for this, but figured I would give it a shot.

I'm looking for some sort of motion-activated audible alarm that is battery powered and relatively small.


I'll explain further.  We're taking a 2 week trip this spring using just our truck.  We have a roof top tent and will carry all of our supplies in the back of the truck under a cargo net.  On the days we are not driving or camping, we will be visiting a number of sightseeing locations and will leave the truck unattended from anywhere between 1-8 hours (possibly more, but I don't think so).  The most expensive items (like our 12v refrigerator) will be locked up in the cab of the truck, but the loss of any number of other items from the bed of the truck would put a significant dent (financial, logistical or morale) in our plans.

My idea is to take one or more alarms and install them so that they trigger if anyone attempts to remove or even reach into the bed of the truck.  I have a couple of ideas on where to install them (such as to the bed rack, under the tent, facing into the bed of the truck) and need them to be battery operated so I can easily replace the batteries daily if needed.  It needs to be loud enough to draw attention in a wide radius.  I don't expect it to deter a determined thief, but hopefully anyone looking to poke around for things of interest will be scared away and decide it isn't worth the effort.


I'm open to specific product suggestions as well as ideas contrary to my plan.

I would worry wind on the tarp would set off a motion based alarm


















 

Yep, wind could be a problem.

I have seen self-contained, battery-powered intrusion alarms that are intended to be used with a single door or window switch. Typically, the switch is a conventional magnetic reed switch, and is used with a magnet mounted on the moving part of the door or window The alarm unit is usually mounted somewhere near the reed switch, and is armed or disarmed with a built-in key switch or keypad.

If the alarm is capable of using a nomally-closed type reed switch, this switch could be replaced in your application with a long, thin piece of wire, looped through every item you want to protect. Then, if the wire was cut or otherwise broken by thieves, the alarm would sound.

+1  There are a lot of switch (contact) types out there, and most security-system switches are normally-closed; ie, the circuit is closed when the magnet is in position relative to the switch, and opens when the magnet and switch are moved apart.

Hmmm...its a cargo net and not a tarp, and it is strapped to the rails of my bed rack extremely tightly.  When you pull on it, it snaps kind of like a guitar string, but its a valid point.  I could hook it up and give it a try and see how sensitive it is to movement from the wind without it held tight against the cargo - I guess that would be a worst case scenario.


The contact alarm is an interesting idea, but I'd like to be able to turn the alarm off and then dig in the bed for something I need without having to work about wires.  With kids, what we need is always invariably somewhere in the bottom of all our cargo.

ETA - it looks like this, only much tighter

If you were to do something like that picture, I'd get some big containers you can put padlocks on, then chain those boxes together.

Something like: http://www.homedepot.com/p/Husky-48-in-Job-Box-BMJB4824/203645735

That's a good idea, not sure why I didn't think about chaining things to the bed mounts.

As always, some of the best ideas are usually some of the simplest.  


I'd still like to look into the alarm.  I'd rather scare them away before they even realize it is tied down if possible.

I have one of these on my Tundra.

I've had one of their "Pro" models on my Frontier for several years, and like it a lot.

The slats are powder-coated aluminum extrusions - each one rides on its own pair of roller bearings.



It is indeed spendy, but it'll probably outlive the truck.

Can't do anything like that.  My bed rack already occupies that location.

I like these.



They can be tied together with a cable and secured with padlocks. About $20 @ piece at lowes or home depot.

hello, I got a cheapie driveway -motion sensor at harbor freight for 15$  have it aimed at my drive by the house. the beep is pretty loud on low.

I'll take a look, thanks.


For those recommending locking/cabling storage containers, is it overkill to lock the containers / have locking containers if I cable them to the bed of the truck.

Not much is overkill when you sit and wonder about losing stuff you do not want to lose.



If you are going with containers cabling them to keep them in the truck is step one, locking them to keep them shut while in truck is step 2, a big piece of plywood or something sitting on top of them and making a big cheap trunk out of the bed of your truck might be step 3.



Plastic is easy to cut open on the sides or top so anything exposed could have a hole cut in it and stuff removed that way.



I would run searches and learn about some of the cable locks stores use on their merchandise.  The little spiderweb one that goes off if someone is pulling at it is what I am thinking of.  It does not care if it moves around, moving whole package to buy it at a checkout, but start messing with the little cables and I believe it goes off.



The little spiderweb would be attached to the cargo net in my thinking, might need more than one.



One thing I could somewhat see doing is running some coated cable or chain over top of the stuff once strapped down.  I had a tarp rip up on one long highway trip and taking the tow chain out of its ammo can and using it to help weight down the tarp pieces that were left helped a lot.