Solar powered, wireless webcam
Everybody loves their webcams (though the surveillance aspects of some are to be worried about.)
What about a way to make them cheap and easy to put in cool places. Combine a webcam with a solar panel, 802.11 link and small bettery. The webcam charges the battery off the panel, and when there is enough charge to take a picture, it takes one and spits it out the wireless link. You don't need much of a battery or much of a solar panel, because the amount of power simply controls how often it can take a picture.
When the sunlight is bright, it's taking pictures frequently. When it's cloudy, they are less frequent. When it's dark, it's not taking them at all. (Though a unit with larger battery could do even this.)
These devices could easily be stuck on mountaintops, antenna towers, roofs etc. The only issue -- keeping the lens clean. Possibly a wiper (fired when blur is detected or manually) or occasional service. A little protection from the rain and wind for the lens of course.
And now that megapixel sensors are so cheap, why not produce a 1280x720 HDTV image, which people can stick on their new plasma screens on the walls, sampling images of the world?