The World Health Organisation (WHO) released a fact sheet about these issues, shortly after the IARC re-classification, entitled "Electromagnetic fields and public health: mobile phones". The fact sheet points to the findings of the IARC and describes some of the known short-term and long-term effects of phone use, but ultimately, it lands on the side of where the most conclusive evidence exists:
These cases work by redirecting the electromagnetic radiation (EMR) that is produced by phones, away from the user. All phones produce EMR when connected to the mobile network, and the effect of this energy is measured as a Specific Absorption Rate, or SAR: a measurement describing the radiation absorbed by kilogram of tissue. Government regulations in Australia dictate that all phones in Australia must emit a SAR less than 2 W/kg under the worst case scenario, and while all phones comply, most modern phones emit, at most, only half of this safe level, or approximately 1 W/kg.
A study by the Corporate EME Research Laboratory and Motorola Florida Research Laboratories tested 9 different cell phone radiation shields, 5 of which claimed to block 99% of cell phone radiation. The other 4 shields tested claimed to emit a reverse radiation that would cancel out the harmful radiation from cell phones. The study found that all of the radiation shields had no effect on the amount of radiofrequency radiation a cell phone user is exposed to from their phone.[2]

Exposure to ionizing radiation, such as from x-rays, is known to increase the risk of cancer. However, although many studies have examined the potential health effects of non-ionizing radiation from radar, microwave ovens, cell phones, and other sources, there is currently no consistent evidence that non-ionizing radiation increases cancer risk in humans (2).