Number Seven: The new robotsWhen they started iRobot Corp. in 1990, MIT grads Helen Greiner and Colin Angle knew they wanted to build robots; theyd figure out their business model later. Did they ever. The Roomba vacuum arrived in 2002, the first truly functional robot to find its way into American households. Last year it earned iRobot more than $400 million in revenue. On a more serious note, iRobot developed a reconnaissance robot for the military. PackBot acts as eyes and ears for troops and neutralizes roadside bombs, screens vehicles and people for devices, and goes into caves. iRobot has built about 3,500 PackBots for US troops in Iraq and Afghanistan.