Not much to it, really. It became feasible around 2007-2008 ish or so, when you could buy glass ampules with rfid tags in them and simple readers retail online (my timing might be a few years off). There were several forums about it at the time, most of them gone now it seems; I suspect because people found out the same thing I did, that it's just not that useful and that the novelty wears off after the first 5 times you wave your hand over a reader and have a led go on or a dialog pop up on a screen.

I went to a piercing study, girl stamped a hole in the upper layers of my skin, made a small cut to open it up a bit further, slid in the ampule (which had been autoclaved first of course). Band aid on it, done. It was strange being in a studio with a bunch of people with facial tattoos and horn implants and discs the size of my wrist in their ears - and them looking at me like I was a freak from out of space. I do have to say though that I had to search around a bit to find someone willing to do it. There are plenty of places that will take your money to suspend you from their ceiling with flesh hooks in your back, but that won't stick a glass pill under your skin. Go figure.

You can also buy kits online if you want to DIY - basically big needle guns that are used to tag cattle which you just jam into your hand and pull the trigger on, literally. That would've been a bit too hard core for me, tbh.