Anybody remember GDW's 2300 AD? I had both versions, as well as the space combat board game. While I loved the setting I never actually got to play it. I've never been able to get a science-fiction game off the ground (not counting cyberpunk), probably because I was intimidated by the scale (and too fond of swashbuckling melee combat). But I did love the hard science-fiction setting. Aside from the obligatory faster-than-light breakthrough (which was handled particularly well), most of the tech was based on conservative extrapolations of existing technology. If anything, these extrapolations were too conservative, but that just made the setting feel that much cooler. It was possibly the only RPG setting that came close to capturing that Aliens feel.
Why bring up 2300 AD? Well, I remember that they had this soft body armor that would harden upon impact by kinetic energy weapons. This article in Business Week talks about how it may soon become reality.