Once in a while, there are news stories about freaks such as Kevin Warwick who put semiconductor chips inside their bodies and call themselves cyborgs. Of course, this activity is still in a state of infancy, but I suspect it is going to be quite popular in a couple of decades. The pioneers want memory expansions, artificial computing features, brain-to-brain communications links, enhanced senses etc. and the transhumanist movement preaches about a new era of enhanced mankind.
Of course, there are all the obvious dystopian consequences I'm not going to list here, but there's also one reason why I'm waiting for this trend: the inevitable counter-phenomenon. You know, the vast increase in the number of people who want to show off by doing the same tricks with the "original hardware", without cybernetics of any kind. I'm thinking about something analogous to what has happened on the demoscene: people do fancy graphical effects with the latest hardware, which inspires some other guys to do the same things with "obsolete" devices.
One computerish feature some people desire for their brain is the calculator. Most people are able to do some very simple calculations in their heads, but two- or three-digit numbers already make them grab a pocket calculator. Clueless people therefore regard this as the limit of the normal human mind, and anyone with much better skills is considered to have some kind of glitch in their brain. Autistic savants and the stuff, you know. By the way, the current unofficial world-record for mentally extracting the 13th root of a 100-digit decimal number is 3.6 seconds, and as far as I know, Alexis Lemaire is not autistic or even a cyborg.
It does seem that fast automatic mental calculation (with no conscious effort) is pretty much attainable by anyone with some proper training, although the methods work better for children than grown-ups. The main trick is that you program the algorithms in the procedural memory area of the brain rather than trying to execute them consciously. In an old Chinese/Japanese technique known as anzan, you first use an abacus for initial programming and after that you visualize a "virtual" abacus and use it instead. In Japan, there are even official examinations (with kyu and dan ranking levels) for abacus calculation and anzan. Some anzan-trained guys tell that they just have to look at a mathematical expression and the result comes to their mind immediately, without conscious effort.
The power of abacus is often underestimated in the West, where it is considered just a primitive mnemonic tool or a children's learning aid rather than a symbiotic device capable of extending one's mental capacity. Some years ago, I bought myself a Chinese abacus and noticed that the bead-movement algorithms tend to automatize in the brain much better than, for example, the algorithms of pen-and-paper calculation. With similar techniques, it might even be possible to build subconscious Turing machines in the brain, programmable via sensory input. Video games would be nice for training the procedural memory to do the required tricks, especially for the current ADHD generation.
There are many, many other interesting concepts for brain-hacking. I'm sure many people are familiar with them, but I'm listing some of them here just for reference:
Mind Hacks is a newish popular-scientific book on many related subjects.
Some Tibetan monks use a hard-core meditation technique called gtum-mo to generate bodily heat.
I want a neurobiofeedback machine some day, for gaining conscious access to some subconscious mechanisms. These things are usually expensive, but there are some guys who have come up with much cheaper EEG designs.
And all right, I also want to believe that there's a hidden telepathy mechanism in the brain, so that we wouldn't be needing those RF transceiver implants either.