The increasing number of electronic devices on our body and embedded in our body have spun research on ways to have them communicating one another and with a gateway (usually a smart phone).
So far the usual approach is to have each of them using Bluetooth. The drawback is the strain put on batteries, since Bluetooth requires quite a bit of power (relatively speaking).
Other approaches, still at research stage, have pursued the use of the body as a conductor and the transmission of high frequency electrical signal on the skin (which is a good conductor for high frequency electromagnetic signals). An alternative approach was proposed using capacity based electrical signals, also known as Body Area Networks, BAN. Both of them suffer from the high path absorption of the electrical signals if you need to connect with devices that are not on the skin but embedded in the body.
At San Diego University a PhD student is experimenting with magnetic based communications that would overcome the shortcomings of electrical communication on the body providing a path absorption that is 1/millionth of the one suffered by electrical signals.
So far he has demonstrated the feasibility of this kind of communication, however (there is always a ... however) to establish the magnetic field one has to wear a sort of bracelets since the magnetic field generation and reception requires a circular "antenna". Your watch wristband would do nicely but it would not work for a sensor in the form of a patch on your skin.
In my mind I see an evolution of BAN integrating a variety of technologies, each one serving best a certain purpose. At least for the coming two decades. Beyond that it is difficult to say, although entering the science fiction space one could imagine a wired body becoming a sort of a printed board onto which a variety of devices can be plugged in... A bit scary for sure, for my generation at least.