Concept: Virus Tech
In the near future, most medical technology revolves around artificially created viruses. Viruses specifically catered to the individual that target all sorts of issues, from aging to the common cold.
Say one day you wanted to change your hair color, eye color, or skin color. A quick trip to the salon, and the tech injects you with a new virus that in short order changes your color.
Or what happens when you get older? Another quick trip, this time to a clinic, and you could get another virus that repairs your cell structure to revitalize your youth.
You could even take this concept a step further. Say, mix this with nanotechnology. For example, a transgender person could have a virus that changes their DNA and cell structure, while nanobots could slowly alter their actual physical characteristics such as bone mass and shape.