Pertinent to a very recent post , UCLA has announced an allergen testing device that attaches to an iphone.

Medical devices that attach to smart phones are becoming more commonplace. What most of these devices provide in terms of power and convenience, they lack in elegance. For devices that couple with something as personal as your phone, much more attention needs to be put into industrial design. This is an opportunity for companies seeking to capture market share for these innovative new devices.
Thanks to Medgadget for the initial reporting on this.