Not all my ideas will be about umbrellas but it just occurred to me that a standard umbrella with the same material (but transparent) gathered like blinds around the rim could be quite handy. When it sleets as opposed to showering, press a slider switch in the handle down and the see-through blinds lower to the level at which you remove pressure to leave you dry in a variable-droplevel tube. When the sleet stops, slide the switch up and the tube returns to its original position around the umbrella rim. When putting the umbrella away, it would be a little bunchier but should still fold up properly.
-- Nelipot, Mar 28 2009

random, halfbakery