Here's one we almost missed: last month a Caltech press release announced the development of a radar-on-a-chip. Ali Hajimiri, Hossein Hashemi, and other researchers at the Caltech High-speed Integrated Circuits Lab found a way to replace the moving parts normally required for a radar with an integrated phased-array antennae (PDF format) and, combined with chip technology that can run at 24 GHz, they produced a working radar on a silicon chip that can be fabricated with conventional photolithography. Companies like M/A-COM and Valeo already sell relatively small, inexpensive automotive radar systems. Mass production of a radar chip for automotive use should bring the cost into a range suitable for robot builders to add radar as a standard sensor. A recent New Scientist story has more details about the new radar technology.