Your cell phone is tracking you, you know. By law, your phone has to tell where you are within 125 meters when you call 911, which isn't so bad on the face of it. However, the telecom systems can use your phone to track you at any time. In some cases, this can be done even when your phone is off. We're not sure how you feel about it, but we don't like being fitted with a radio collar at all times. This nonconsensual tracking is growing common in the US now, but has been around in Europe for quite a number of years. So what's a paranoid to do?
Your best choice is to not carry a cell phone. Yanking the battery from the phone works too, and is slightly more convenient. We here at the BBC (No Relation) were pondering this problem and it dawned on us that we already had the technology to solve this. Aluminum foil. The basic technique has been tested to perfection by countless shoplifters: all you have to do is wrap your phone in foil, and then radio transmissions are blocked! It's like a TAZ for your phone.
Still, carrying your phone around in a big wad of foil isn't quite as convenient as it could be, so we refined the idea into a little something we call The Invisifier. When you place your phone in The Invisifier, radio transmissions are blocked. This not only stops the phone from telling someone where it is, but it prevents the phone from even being able to know where it is.
Obviously, you can't place or receive any calls when the phone is in there -- it's invisible, after all -- but it does restore a little lost privacy by letting you choose when and where you allow the system to find you. If you're into that kind of thing.
Why would you care, unless you're some kind of criminal? Well, even ignoring the plain historical fact that every surveillance power we have ever allowed the government has been egregiously abused, there's the fact that it's not just the government who uses this information. There are few restrictions on what the telecoms can do with it, and they're interested in all kinds of groovy things like sending you spam advertising that italian restaraunt you're approaching. And let's not forget the cool uses that private investigators, crackers, and technologically literate criminals find for it.
How to Build One
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Take a square of aluminum foil and fold it in half. Traditionalists should ensure that the SHINY SIDE IS OUT, but others won't care about that. The resulting rectangle should be roughly 1.5 inches taller than your phone, and roughly three times as wide as your phone. The width is less critical, you can trim it down to size later.
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Position the foil so that the fold is at the top. Apply a strip of duct tape across the foil, lined up with the top. Apply another strip below that, overlapping slightly. Keep working down until you have covered all of the foil except the bottom half inch or so. You should have something that looks like this:
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Turn the foil/tape concoction over so the taped side is against the table with the edge you left bare on the left. Now, apply more duct tape as you did before, working from the top down, only this time leave a half inch or so bare on the right side. It's easier if you overtape on the left side and trim later. When done, you'll have a double-thickness of foil with duct tape on both sides. It should look something like this (before trimming):
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Fold the exposed aluminum strip that has the fold, so both strips on the same side:
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Turn the sheet over (so the exposed aluminum is underneath). Take your cell phone and roll it in the sheet. You want it a little snug, but loose enough so the phone can pass through the easily:
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Cut off the excess part of the sheet and use a little piece of tape to hold the tube together temporarily. Take a moment to shape the tube into a rough rectangle and double-check the fit with your phone.
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One end of the tube is where your initial aluminum sheet fold is and the other end will have two leaves of aluminum foil. You want the end with the two leaves. Cut slits in each of the corners so that the exposed aluminum forms flaps:
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Each side of your tube now has two flaps -- the innermost flaps are foil with duct tape stuck to it, and the outermost flaps which are just foil. Fold all the innermost flaps in first, then fold the outmost flaps over the top. After this step, the end of the tube should be completely covered by foil. If that's not the case, you can fix it by placing a small piece of foil over any holes.
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Seal the end with some duct tape. Your tube should now look something like this:
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Make the lid for the case. Cut a square of aluminum foil that is about 1/2 inch larger than the opening of the tube on all sides (you want this large enough so that the lid covers the exposed aluminum at the end of the tube. Place this over the open end of the tube and pinch the corners like so:
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Fold the corner flaps over the narrow end of the tube, like wrapping a present. This pic sucks, but it should give you the idea:
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Seal this end with duct tape as well, but be careful: don't attach the duct tape to the tube itself! Just form-fit it, then take the assembly off the tube. Trim the duct tape so it extends about 1/16 inch past the lip of the foil. Fold it around the lip to protect it from wear when you put the lid on. The important point is that there must be good electrical contact between the lid and the body of the case.
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Carefully fit the lid back onto the body (don't crinkle those narrow unreinforced sides!). Wrap narrow strips of duct tape around the outside of the lid, being sure to cover the exposed foil sides. With the lid still on, use another piece of duct tape to seal the side seam on the body of the case. Your Invisifier is technically complete!
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TEST IT!
Testing is very easy. Turn on your phone, put it in the Invisifier, put the lid on snugly, and try to call it. If you can't get through, then it works! If it doesn't work, it's either because there is a gap in the foil coverage somewhere, or because the lid and the body are not properly electrically connected. The exposed aluminum around the opening of the body must contact the aluminum inside the lid.
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Decorate it as desired.
The Invisifier will eventually wear out as the foil will develop cracks after enough handling. It's only duct tape and aluminum foil, after all. It's a good idea to test it prior to each use to make sure it's still working right. You could make the same thing more permanent by using thin sheets of copper (found at any hobby shop) intead of foil, if desired.