The same thing is happening with the drivers and gunners on armored trucks that travel frequently through dangerous parts of Iraq. In addition to the bulletproof vest, there are now additional bits of Kevlar material for the upper legs and arms. This provides protection from the blast effect of roadside bombs (IEDs), and the many small fragments (like gravel) that they generate. The extra weight of this additional armor is not a problem for the troops manning weapons, or driving the vehicles. Many of these vehicles are also air conditioned, which means the additional armor does not increase the heat shock risk.
For infantry, however, there are improved versions of the decade old SAPI, bullet proof ceramic plates. This is the Dragon Skin armor, which uses smaller bullet proof plates (about 40mm wide) that are arranged like fish scales. This was a popular type of armor in ancient times. This sort of thing provides flexibility, as well as slightly superior protection to the current large ceramic plates. A big advantage of the Dragon Skin scale armor is that it can cover more area, providing increased protection against high powered rifle bullets. The only problem with the new armor, aside from up to eight pounds of additional weight (depending on how many of the small plates are used), is that it cannot be manufactured quickly enough to replace the hundreds of thousands of older type vests already in use. The Dragon Skin plates are more difficult to make than the existing SAPI plates, and it will take months, or years, to refine the manufacturing process. The situation has produced a PR nightmare for Department of Defense bureaucrats who will, and are, taking a beating for not solving this problem (no excuses, not matter how reasonable, are acceptable in situations like this.) However, the usual sense of wartime urgency has gotten the new personal armor developed and into production much more quickly than would have been the case in peacetime. Long term, this saves the lives of many troops.
One of the many technical innovations coming out of the Iraq war are several new types of body armor (protective vests) worn by the troops. For example, truck turret gunners in Iraq are adding more bits of personal armor, repeating a pattern first encountered over sixty years ago, during World War II. Back then, the most dangerous combat job for Americans, at least until mid-1944 (when the Allies invaded France), was as a crewman on a heavy bomber flying missions over Germany and occupied Europe. The major threat was, as it is in Iraq, exploding shells. The bomber crews often had to fly past dozens of exploding 88mm and 105mm anti-aircraft shells. The bombers were not armored, but the crews were. The first modern protective vests were developed for these men. The flak jackets were too heavy to easily move around in. But for aircraft crew sitting down, or even for the waist gunners who stood while firing their .50 caliber machine-guns, the weight was bearable. In addition to the flak (named for the German abbreviation to anti-aircraft cannon) jackets, some aircrews added more armor to legs and upper arms.