Geiger counters are to become next sensor to be added to iPhone 7 i guess. A health app counting you daily calories and roentgens. Or an augmented reality app which shows the sources of radiation, like those vans, around you.
Geiger counters can also detect XRays more or less effectively depending on their design.
> Ionizing radiation is any type of particle or electromagnetic wave that carries enough energy to ionize or remove electrons from an atom. There are two types of electromagnetic waves that can ionize atoms: X-rays and gamma-rays, and sometimes they have the same energy.
http://physicscentral.com/explore/action/radiationandhumans....