Human Area Networks are just a name for using human skin (while the human is alive) as a transmission medium.
But to me, the most exciting aspect of communications over human skin is that it gives communication devices "context".
So a post-it note stuck to nothing that says "trash me" will mean just the same action as a piece of paper that says "trash me". But when a post-it reading "trash me" will mean different actions when stuck on a book versus a cabinet.
In the same way, devices in the vicinity of each other can communicate, but it has no context other than geographic closeness (which sometimes is enough). But with communications over skin, it gives the context of an intent by the human to interact with the device they're touching.
This kind of thing could be applied to "needies"
Which are "attention-starved stuffed animals" Each one knows when they're being touched, and broadcasts that information to other needies in the room. The ones that aren't being touched will complain, and say things like, "hug me instead!", or "Throw him! Throw him!" So instead of always broadcasting, they will have extra information about the state of the world by which medium they can communicate through.
As another inane example, personal devices being held by the same person running a screensaver can have fish swim from one screen to another screen of a personal device.
Again, the medium of human area networks gives the communications context by human intent, rather than just by geographic vicinity.