There is no strong or consistent evidence that mobile phone use increases the risk of getting brain cancer or other head tumors. The United States National Cancer Institute points out that "Radiofrequency energy, unlike ionizing radiation, does not cause DNA damage that can lead to cancer. Its only consistently observed biological effect in humans is tissue heating. In animal studies, it has not been found to cause cancer or to enhance the cancer-causing effects of known chemical carcinogens." The majority of human studies have failed to find a link between cell phone use and cancer. In 2011 a World Health Organization working group classified cell phone use as "possibly carcinogenic to humans". The CDC states that no scientific evidence definitively answers whether cell phone use causes cancer.[5][7][8]

In 1993, the cell phone industry was pressured by Congress to invest $28 million into studying cell phone safety. The cause of this sudden concern was massive publicity about a lawsuit filed by Florida businessman David Reynard against cell phone manufacturer NEC. Reynard’s wife, Susan, died of a brain tumor, and he blamed cell phones for her death. Reynard revealed the suit to the public on the Larry King Live show, complete with dramatic x-rays showing the tumor close to where Susan held her cell phone to her head for hours each day.
Dr. Carlo, wrote a  Medical Alert ten years ago. He cautioned people with EMF sensitivity against relying upon widely-available EMR Protection Products to prevent the effects of EMF exposure. He noted that EMF sensitive individuals were reporting the opposite effect: people found their symptoms and/or sensitivity worsened. Specifically, severe “symptom relapses.” Dr. Carlo noted:
The use of "hands-free" was not recommended by the British Consumers' Association in a statement in November 2000, as they believed that exposure was increased.[41] However, measurements for the (then) UK Department of Trade and Industry[42] and others for the French Agence française de sécurité sanitaire environnementale [fr][43] showed substantial reductions. In 2005, Professor Lawrie Challis and others said clipping a ferrite bead onto hands-free kits stops the radio waves travelling up the wire and into the head.[44]
You hit the nail on the head when you say that distance is key when it comes to EMF exposure. The solutions you sell will definitely help provide that separation. That said, our products are different in that they shield the user from EMF while allowing them to use the device as they normally would, without needing to hold their device by a rope or placing it in a faraday cage that eliminates signal altogether.
A 2010 review stated that "The balance of experimental evidence does not support an effect of 'non-thermal' radiofrequency fields" on the permeability of the blood-brain barrier, but noted that research on low frequency effects and effects in humans was sparse.[4] A 2012 study of low-frequency radiation on humans found "no evidence for acute effects of short-term mobile phone radiation on cerebral blood flow".[5][6]
I noticed the Blocsock hardly added any bulk to my phone, and fit comfortably in my pocket. I have a Rocketfish RF-MTVT2SP protective gel case and thankfully the phone fits the Blocsock without having to take off this case. The Blocsock is very easy to use, and is quick and easy to take out and answer the phone. Again, if you get one, make sure the size you order is right and not too tight or loose. The pouch on the Blocsock is handy when using the phone to call people so the phone can be placed in the pouch between the Blocsock and me, protecting my head from radiation while still enabling people to clearly hear me and vice versa.
The peer reviewers did have some quibbles with the study; some wished it could have lasted longer (the rodents were exposed to radiation for two years) to catch later-developing tumors, for example, but others on the panel noted that the longer a rodent lives, the more likely it is to develop tumors regardless of radiation, making it harder to find the signal in the noise. Others wanted the researchers to have dissected the rodent brains more than they did, to seek hard-to-find tumors. But they noted that science is an iterative process; the study wasn’t perfect, but it’s better than anything that’s been done so far.

There's a lot of talk in the news these days about whether or not cell phones emit enough radiation to cause adverse health effects. The concern is that cell phones are often placed close to or against the head during use, which puts the radiation in direct contact with the tissue in the head. There's evidence supporting both sides of the argument.

Cell phone radiation refers to radiation in the form of electromagnetic waves that is emitted from mobile phones. This type of radiation takes the form of radio waves that are near the microwave range. The amount of radiation that a given cell phone will emit depends on the exact frequency of the radiation, as well as whether the device is using an analog signal or a digital one. There has been speculation that large amounts of cell phone radiation could be hazardous to the user's health, but there are no conclusive scientific findings on the subject.
Read the “fine print” from the manufacturer’s instruction manual which tells users to put a distance between the phone and your head and body. These fine print warnings range  from a few millimeters to almost an inch. The fine print warnings on other wireless devices (such as Wi-Fi routers, wireless printers, home cordless phone base stations and baby monitors) generally state the distance should be at least 20 cm, or about 8 inches. If people are closer than the manufacturer stated separation distance, then they can be exposed to RF levels that violate the US government FCC limits for this radiation.
Today there are more than two billion cell phone users being exposed every day to the dangers of electromagnetic radiation (EMR)—dangers government regulators and the cell phone industry refuse to admit exist. Included are: genetic damage, brain dysfunction, brain tumors, and other conditions such as sleep disorders and headaches.1-9 The amount of time spent on the phone is irrelevant, according to Dr. Carlo, as the danger mechanism is triggered within seconds. Researchers say if there is a safe level of exposure to EMR, it’s so low that we can’t detect it.

Well, Loyd really does seems like a guy with great intentions! However, he has put too much faith in Pong’s SAR testing, and SAR guidelines in general — to the point he no-longer believes his own eye’s when nothing is observed on his trusty RF meter.   Which proves (Using an RF Meter) there is absolutely no real reduction in actual radiation coming from the front of the phone when a pong cell phone case is used.

Just as inevitably, worries about brain cancer spawned a market for products that supposedly protect cell phone users. For $62, you can order a Delta Shield, a thin polyester patch that contains a microchip that allegedly renders cell phones harmless. Users are instructed to place the patch on their cell phone battery. The similar BIOPRO Cell Chip, sold online for $35, attaches to the outside of the phone. The penny-size WaveShield 2000 Gold, selling for about $25, fits on the earpiece.
The authors found a consistent effect, in both types of studies, that cellphone radiation leads to decreased sperm motility (ability to swim) and viability, but not a decrease in overall concentration. While it’s unclear if these specific changes are enough to affect men’s fertility, the authors wrote, “mobile phone exposure may form part of a cumulative effect of modern day environmental exposures, that collectively reduce sperm quality and explain current trends in infertility.”

The first one is easy, cellular frequencies vary between 450–2000MHz, but 800 or 900 MHz is the most common. The power emitted by a cell phone varies over the course of the call (higher when making initial contact, which lasts a few seconds). It can go up to 2 Watts at the start of a call, and can go down to .02 Watts during optimal operation [2]. Of course, most people barely use cell phones for calls, but I am using this example as a worst case scenario, because the phone is not right by your head when you are browsing Tinder.
Radiofrequency radiation is a form of electromagnetic radiation. Electromagnetic radiation can be categorized into two types: ionizing (e.g., x-rays, radon, and cosmic rays) and non-ionizing (e.g., radiofrequency and extremely low frequency, or power frequency). Electromagnetic radiation is defined according to its wavelength and frequency, which is the number of cycles of a wave that pass a reference point per second. Electromagnetic frequencies are described in units called hertz (Hz).