I bought one of these to keep in the car as an emergency shelter/waterproof

http://www.ddhammocks.com/product/poncho

Absolutely superb, it’s massive, works great as a poncho and brass eyelets at corners should make it a superb temporary shelter. Completely waterproof living in the uk and this being summer it’s been tested in some torrential downpours, the only downside is it’s quiet heavy and doesn’t pack down as small as the cheapo festival ones but for anyone out in the woods etc hard to beat IMO.