So, what types of RF are these cases intended to block? If they block the frequency being used by the phone than if the blocking is complete the phone won’t work. If it’s partial than, as noted by the FCC and related in the article, the phone may attempt to compensate for the weakened signal by increasing it’s signal strength, thereby emitting higher levels of radiation itself, and reducing battery life in the process.
The next scientific step will be to determine what this means for humans. The peer-reviewed papers will be passed on to the US Food and Drug Administration, which is responsible for determining human risk and issuing any guidelines to the public, and the Federal Communications Commission, which develops safety standards for cell phones. The FDA was part of the group of federal agencies who commissioned the studies back in the early 2000s.

It'd be wrong to say that there is no evidence of harm at all. In fact, the re-classification by the IARC came about in the first place because the Working Group contributing to the Interphone study acknowledged "limited evidence" of an increase in glioma (a type of tumour, commonly found in the brain) among phone users in one of the studies. In this study, which concluded in 2004, researchers found that participating phone owners who had used their handsets for calls for more than 30-minutes a day, over a period of ten years, had an increase incidence of glioma.
This was the best vegan EMR-blocking phone case .... I need to carry two IDs and four cards plus cash.. This was too much, so it started to split within months. Eventually it split to the point where my cards would all fall out if I tipped it the wrong way, so I had to put a rubber band on it. After that, the part that holds the phone started to slip so I have to jam it up before I can take a picture. And the case is looking worn. The upshot is that it lasted about a year. That's fine, I guess, but I would prefer something more durable.
Since 2011 RF radiation has been classified as a Group 2B “possible” human carcinogen by the International Agency on Cancer (IARC), an agency of the World Health Organization. Based on the new animal findings, and limited epidemiological evidence linking heavy and prolonged cell phone use with brain gliomas in humans, Fiorella Belpoggi, director of research at the Ramazzini Institute and the study’s lead author, says IARC should consider changing the RF radiation designation to a “probable” human carcinogen. Even if the hazard is low, billions of people are exposed, she says, alluding to the estimated number of wireless subscriptions worldwide. Véronique Terrasse, an IARC spokesperson, says a reevaluation may occur after the NTP delivers its final report.
Regular battery-powered watches (and all other battery-powered tech, for that matter) also produce some level of EMFs, but that level is far lower than the amount emitted by tech devices that are plugged in, or that receive and transmit information wirelessly. The same rule applies however; if you can turn it off and keep it away from your body, then do so whenever possible.

Let’s be honest, we’re addicted to our smartphones. According to an ABC news report, the average person checks their phone 150 times per day, not to mention the other 15 hours per day it sits in your pocket. It’s also nothing new that cell phones emit Electromagnetic Fields/Radiation (EMF/EMR) when it’s glued to the side of our head more than 22 times per day. 

Generally, the Ministry of Health adopts the instructions of most international entities, recommending to follow the “precautionary principle” regarding mobile phone use. The instructions of the Ministry take into account the technological need of the population in Israel, along with the measure of precaution necessary according to the recent scientific information in order to balance between the population’s needs and the preservation of its health.

Remember: The cancer incidence data in humans, at least to date, suggests no avalanche of head and neck tumors. Since so many people are exposed to cellphones, if there were a big risk, we’d probably see it turn up. “If cellphones caused brain tumors at the rate that cigarettes caused lung cancer,” said Otis Brawley of the American Cancer Society, “we would have figured it out by now.”
Moving the meter around the case, we detect readings on the side, back and front of the case. We use the multi-directional TES 593 meter which measures 10 MHz to 8GHz. We use the unit of micro-watts per square centimeter, which looks like this little symbol: μW/cm² and we use it on the max setting which shows the maximum measured value. In non-science speak: the highest level of RF we see, which could be from the back the side or the front. 
If not, then how can the seller claim that the reported effects on cell cultures, muscle strength testing, plants, skin heating, or other biological effects are due to electromagnetic changes (see for example)? Electromagnetic field characteristics are well known and easy to measure. If there is truly an electromagnetic change, that change will be easy to detect and measure.
In subsequent analyses of Interphone data, investigators addressed issues of risk according to specific location of the tumor and estimated exposures. One analysis of data from seven of the countries in the Interphone study found no relationship between brain tumor location and regions of the brain that were exposed to the highest level of radiofrequency radiation from cell phones (9). However, another study, using data from five of the countries, reported suggestions of an increased risk of glioma and, to a lesser extent, of meningioma developing in areas of the brain experiencing the highest exposure (10).