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.