One of the most advanced wearable projects has stopped now, the land warrior. Time seems not to be right for the whole bunch of technologies planned. But a few became "part of the process". One of the biggest challenges is still power cause batteries where not powerful enough. Communication in the meaning of "always one" wold be important but is still not 100% reliable.

Just a little piece from this interesting must read:

Land Warrior tried to give each infantryman a wearable computer, using an eyepiece as a display (attached to the helmet, and flips down for use), and a small keypad to control the thing. GPS puts the soldiers location on the map shown in the eyepiece. Tests so far have shown that this works, but not well enough to withstand the rigors of the battlefield.

Meanwhile in Iraq, infantry officers and NCOs, equipped with PDAs, have found the map/GPS combo a tremendous aid to getting around, and getting the job done.

Go on here for the whole story: Infantry: Land Warrior Died For Our Sins