Well looks like interactive/programmable tattoos are pushing forward, about a year or so ago I read about this implant - a small screen with a black and white display on it that ran of chemical energy siphoned from your blood, that was a concept. Now its been pushed further, moving from sub-dermal implants to nano-tubes placed either sub-dermaly or on the surface of the skin but as a custom size rather than a single cohesive pad. This apparently work in a more passive way than the 'screen' in that the electrics are only needed to change the display which is otherwise passive and just sits there.
Still pretty cool and I want one very much. Annoyingly I have three links but the video on the last one won't load for me - have been told that it is semi NSFW:
fun video NSFW