Design milk cartons which have a litmus strip that changes color depending on the freshness of the milk. A face could be printed over the strip - turning green when the milk is spoiled.

Design mirrored nail polish or clip-on nails such that the wearer can check their face discreetly and at any time.

Design cigarettes with strikable tips. The cigarette packet would have an abrasive surface on one of the box faces against which the cigarette would be struck, negating the need for a match or lighter.