Muwi is a next-generation robomower that "calculates the size of the lawn and automatically cuts the grass -- as the grass cuttings accumulate inside the machine, Muwi constructs and compresses them into cylindrical blocks." Click here for first picture in gallery.
The blocks can become balls for children to play with or be combined to make a chair or anything else you can think of. After the blocks are used, they can be left to return to nature.[via Toxel]