It's a 4th edition one brought forward, but, essentially, it's modding your arm so that you can add-in a Medkit of Rating X, allowing it to be carried with you, but also to function easily ... parts rotate, there's a nice viewscreen that you can eyeball, it can interact with other upgrades that you instal (For example, a 'stinger' upgrade and a chemical resivoir or three, letting you do medical examinations and inject things carefully, with teh medkit helping the dosage levels), and so on.
It's *kinda* like having one in a smuggling compartment, but much cooler, just like you can use a normal toolkit, or you canhave a cool cyber toolarm that has rotating bits as different wrenches are needed. (The rating of the medkit depends on what you buy, of course. I suggest a Rating 5 or 6, and it's verymuch intended to be used on other people, but it could be used on yourself with difficulty (About as easy as using a medkit on yourself). Just like having a doctor's bag today, it's one of those things that you can quickly lift, say, "Let me through, I'm a doctor!" and security will let you past in some situations.