There's a lot of major things here.

1) Tattoo is invisible. No stigma attached. 2) No blood drawn for testing for various materials 3) If processing and power get consolidated onto the phone, this will be massively portable and accessible to the masses, assuming they manufacture large quantities of the case.

Currently, the iPhone is basically just a camera chassis. You could achieve the same effect by building a case for your cheap little Canon Powershot, which has the benefit of including a removeable SD card.