We get carried away with the idea of bolting robot arms and legs to our fleshy torsos, but I firmly believe that the real core of what we can innovate lies within our meat - more specifically, in our brains.
Deep brain implants are the way in which the human machine can truly be supercharged. Consider our gray matter; our neural DNA has been imprinted with a mammoth amount of information allowing us to parallel-process huge and complex data sets in quick order - but for all that, our "wet memory" is patchy and sporadic. We lack the ability to communicate data in complete fashion!
Through the use of cognitive enhancement implants providing neurotropic stimuli, we are capable of creating a new level of neural synchrony that can effectively boost brain capacity; and via wireless data-parsing subsystems, a form of "radio telepathy" is a real and viable concept. Faster brains processing more data, reacting quicker, capable of streaming that data in real-time to other similarly accelerated posthumans -- this is the real frontier.