<p>Jay Walker jump-started an online shopping craze by inventing Priceline.com, the Web site that lets people bid on airplane tickets and hotel rooms.</p>
<p>Now Walker is hoping his newest brainchild revolutionizes a completely different field: national security.</p>
<p>The premise behind Walker's USHomeGuard is simple: America has 47,000 power plants, airports and other "critical infrastructure facilities."</p>