Popular Mechanics has a great story about robot penguins being used to study Emperor penguin colonies in their natural habitat without disturbing them.
After discovering tagging penguins with bands around their flippers was harmful—it impaired their survival and the number of their offspring, presumably by reducing their speed in the water - scientists switched to implanted RFID tags.
This presented the challenge of getting close enough to the penguins to read the tags - a distance of roughly 2 feet - without disturbing them. The solution was robot penguins, which can maneuver around penguin colonies without attracting a lot of attention.
This is a great example of sensors and robotics in use.