Do electromagnetic shielding stickers do anything?
I call quackery. You don't want to shield the electromagnetic field, because that's what makes the phone work. If you would stop the EM field you wouldn't have communication.
The "24 carat gold" should also ring a bell. I bet there's not a \$\mu\$g gold in it. Even if you want to make a shield there are much cheaper materials which perform almost as well as gold does, aluminium for instance. Despite what some people think you don't need a magnetic material like steel (iron) to shield off alternating electromagnetic fields. (Besides, gold isn't magnetic either.) For shielding you need a good conductor. Gold is one, but so are copper and aluminium. The magnetic field passing the shield creates eddy currents which in turn create a field countering the first one.
I guess you're supposed to stick it onto your cellphone, and that's supposed to protect you from nasty E-M radiation.
Electromagnetic radiation can be nasty at some energies, but the EM radiation from your cell phone isn't dangerous. Radiation is dangerous as such when it is ionizing radiation - capable of removing electrons from an atom, creating an ion. Ions are chemically reactive, and it's the reaction that causes harm.
Take a look at this image of the electromagnetic spectrum from Wikipedia:
Your cell phone operates between the radio and microwave frequencies. Ultraviolet light (such as that created by the sun) is the lowest-frequency ionizing radiation.
My initial reaction is that this is total quackery, but let me ask those more knowledgeable in the field: is there any substance to these things?
If you're not convinced by or don't understand the ionizing vs. non-ionizing radiation argument, note that visible light is closer to being a "nasty" ionizing form of radiation than radio waves. Don't worry about it.
leftaroundabout points out that radiation can also be dangerous at high frequencies due to thermal effects. However,
- Low power levels,
- Large thermal mass in your head, and
- High conductivity of any thermal effects by your blood
combine to make this a non-issue.
Summary:
The stickers don't help at all
If you care a Bluetooth headset is liable to be the best solution.
It is possible but by no means certain that there are any significant health effects from using cellphones. Very heavy use may be more liable to hurt, but even this is uncertain.
The stick on "shields" do nothing useful and probably nothing even measurable.
You could produce shielding for a cellphone - but for it to have any significant effect on user field strength levels it would have to severely impact the phone's radiation pattern and would have a good chance of affecting how effective the phone was as a communicator. To be useful (if usefulness is in fact needed) and also not affect the phone's operation would require it to be designed for a specific phone's spatial and functional layout.
There is also a prospect that adding "shielding" may make any effects that do exist worse by altering the field shape and maybe causing an area that is more sensitive to have increased exposure. This is extremely unlikely, but worty noting for completeness.
If you must have shielding then the most effective and cost-effective method is either
(1) to use an external antenna. At the distances of phone to body the user is very much in the near field and coupling will be largely magnetic. Magnetic shielding is harder than RF. But, magnetic field strengths drop (notionally) with the cube of distance. If you could move a phone a few hundred millimetres from your head you'd get great reductions in field level. Or
(2) Use a remote connection to the phone - which is what a Bluetooth headset does for you. Bluetooth has its own transmit field but it is very substantially smaller
Even a wired earpiece/microphone will achieve a similar result. You'll get some RF transfer along the wire but it will be much much less than than the affect from close proximity to the cellphone. If a wired headset is used then adding a ferrite RFI shield (eg a purpose designed ferrite toroid or clamp around the cord outer - no electrical connection - would further reduce RF reaching the headset.
But
There has been ongoing effect over many decades re the biological hazards from EM fields. There have been numerous scientific studies and consequent peer reviewed papers that concluded that there were statistically significant hazards in some cases - and about as many others that concluded just the opposite.
One of the more disturbing (to me) was the suggestion that very heavy users developed certain carcinomas in the head, significantly more on the side closest to common cellphone use and overall significantly more than for the general population. BUT I understand that even this claim is subject tonthe normal debate and uncertainty.
My practice and advice in this and similar areas is "prudent avoidance" - do what you can to avoid what may be risk situations but don't let them wreck your life. There is usually not any sensible need to let such things overly even influence your life. eg
If you use a cellphone a lot Bluetooth makes sense anyway.
Locating the mains transformer equipped alarm clock away from your pillow when you sleep is of minimal effort.
Not buying a house near or under HV powerlines makes sense because of what others think as that will affect prices regardless of whether there is any effect or not.
And rental accomodation under a powerline will usually not be cheaper than similar accomodation elsewhere.
If your children have left home and you are older than younger and favor house per $ over resale value then buying under powerlines may make much sense. if there are effects they take decades to manifest and are almost ij the noise when/if they do.
So - ignore the stickers, get a Bluetooth headset (and Bluetooth equipped phone).