Dr. Samuel McConkey:

The uptake at present is approximately 1.7 or 1.9 million, which is only about 34% of the population. The modelling suggests that we need about 60% or more to get a really good impact. It does not work on old iPhones like the iPhone 5 and it does not work on older android devices. It only works on more modern phones. There are older people, like my mother, who still have Nokia block phones and it definitely does not work on them.