Design company Frogdesign imagined the concept of Datoo (DNA tatoo):

The concept of the Dattoo arose in response to current trends towards increasing connectivity and technology as self-expression. (... The idea of DNA tattoos (Dattoos) is to use the body itself as hardware and interaction platform, through the use of minimally-invasive, recyclable materials. (...) All hardware would be created on demand and assembled via a special online design portal. Users view, test-drive, and select their product from a variety of options, both functional and aesthetic. They also set the lifecycle of the product, to be utilized for a few hours or a much longer amount of time. Once users are satisfied with their specific configurations, they have this fully-functioning circuitry - including all UI-interactive and display functions - “printed” onto recommended areas of their skin.

Utilizing future technology, Dattoos have yet to reach fruition. The final concept aims to achieve a convergence of the following capabilities: DNA-reader and identification technology; nanosensors and interactive “touch reading” for finger tips (Braille); pattern and image recognition; self-learning and educational applications; living materials that change shape and feel; flexible OLED displays; full voice interaction, directional laser speakers; bionic nano chips; and cyborg components.

Why do I blog this? though speculative, this concept is curious because he it shows how some current practice (tatoo, personalization) are expanded and applied to the "body as the interface" issue.