For now, it’s probably better not to spend too much of your time worrying: you’re surrounded by cellphone signals, Wi-Fi signals, and all other kinds of radio frequency radiation day in and out — not just when you put your phone up to your face. And until the evidence suggests otherwise, all of this is still considered less of a cancer risk than eating red meat (which you shouldn't freak out about that much either).
Anti-radiation or radiation blocking or phone shield cases. Do they Work? SafeSleeve, DefenderShield, Vest, Alara, Pong, Reach and ShieldMe  and other EMF protection phone cases claim to block the radiation from your cellphone or smartphone. Anti-radiation cellphone case brands make enticing claims like this: ". . .eliminate up to 99% of the harmful radiation coming from the phone!"

Educate yourself about the RF sources in your home, and replace the devices that you can with non-wireless alternatives, and replace the wireless connections that you can with wired ethernet or other cord/cable connections. Note: most wireless devices can connect non-wirelessly, sometimes an easy-to-find adaptor accessory is required to use cords/cables.

Another way to think about the situation is to consider the steady state power emission of .02 Watts and ask how long it would take to heat up your body by one degree Celsius if your entire volume was exposed. Take your body mass to be 100 kg and approximate it as being composed entirely of entirely of water. If all of the radiation was absorbed and went into heating you up (which it isn’t), it would take 20900000 seconds (specific heat*mass*1 degree/power) or 241 days to heat you up by one degree. Fortunately, you have metabolic processes in your body, or possibly air conditioning, to mitigate this heating.
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.

Pong’s research indicates that badly designed cell phone cases can partially block a phone’s antenna, making the device work harder to transmit signals. Due to gaps in the FCC’s cell phone regulations, a phone worn right next to the body and enclosed by a case that obstructs the antenna could expose the user to more radiation than the FCC’s legal limit.
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.
The energy of electromagnetic radiation is determined by its frequency; ionizing radiation is high frequency, and therefore high energy, whereas non-ionizing radiation is low frequency, and therefore low energy. The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency radiation. More information about ionizing radiation can be found on the Radiation page.