Tire inflator kits – 

To save weight (and make room in ever-smaller trunks) many new cars no longer have a spare tire at all. Not even a mini-spare. Instead, when you get a flat, you unbox a tire inflator (and repair) kit, usually packaged under the trunk floor or in a side panel storage cubby. It contains a small air compressor you plug into the car's cigarette lighter – whoops, politically incorrect… meant to say "power point" – and a can of goo, basically, that mixes with the incoming compressed air, shoots into the flat tire – via the stem – and simultaneously plugs the hole and refills the tire.

Upsides: You can get back on the road in minutes, without getting dirty. More room in the trunk for cargo, less weight to carry around and cost you gas. Also, instead of driving around on three normal-sized wheels/tires and one clown-car-sized "temporary use only" mini-spare, you get back on the road with four normal-sized wheels/tires.