American soldiers have a bevy of hand-launched unmanned aerial vehicles to choose from these days, but nothing quite as nimble, lightweight and cheap as the Stevens Institute of Technology’s unmanned helicopter. The chopper would allow soldiers to check tall buildings for enemies by flying the camera-equipped, remote-controlled helicopter up staircases and into hidden corners before they go in. The four-pound prototype is made of a doughnut-shaped fiberglass shell 18 inches in diameter; inside, two counter-rotating 14-inch rotors create lift.

A team of scientists led by V. Ramanathan of the University of California, San Diego have begun using autonomous unmanned aerial vehicles, or AUAVs, to study the link between air pollution and climate change. While some of today's top robot drones are operated via remote control, this new fleet of eight-foot-long, sub-50-pound Manta AUAVs fly all on their own.

Yesterday Boeing announced that one of its pilots recently took to the air in an airplane powered by hydrogen fuel cells. This marks the first time a manned aircraft running on fuel cells has ever successfully completed a flight, though robotic drones have done so in the past.

Two years ago we wrote about Norwegian engineer Petter Muren's effort to build a mini copter weighing only 3.3 grams. that radio-controlled craft, the Picoflyer, could take off from the palm of your hand. Now Muren has designed the larger but more capable Black Hornet.

Behave yourself in Miami, because the eyes-in-the-sky may soon be watching. We're still not sure about all those rumors concerning insect-sized flying vehicles keeping watch over cities, but larger versions certainly seem to be on the way.