I'd love to make money doing something mindless while riding the subway. This dead time is a great opportunity for advertisers to solicit my feedback on logos or other designs.
Games that ask you to identify logos with brand names removed have existed for a while. But, someone should create a mechanical turk-like mobile game that allows people to get paid for giving feedback on logos and brand recognition. Advertisers would pay to be included in the game and that money would then be split between the game creator and users, who would earn the equivalent of credit card points.
For example, this could be a multiple choice quiz to select the right brand associated with a logo. Users would be asked to indicate their selection through a mix of tapping and swiping to make sure that they're paying attention.