I have spent the last four hours reading Heidegger on tools and "worldhood". Did I understand any of it? You be the judge.
Let's say I am one of those soulless drones in the Visa Paywave ad and I "want" to buy lunch, insofar as mindless automatons can be said to "want" anything. But this very mindlessness, while exaggerated, represents the world as seen from the position of Desein, an identity defined by the execution of behaviour in an environment - or, in Heidegger's terminology, Being.
Equipment is required for Desein to have meaning, because meaning is function, and function is founded on invisibility. Here, what is ready-to-hand (invisible) is my Visa Paywave card: I need it to perform my action of buying lunch that defines me as Desein. The equipment (card, Eftpos machine) is invisible, and Desein is therefore stable.
But then some mouth-breathing plebeian tries to buy their lunch with cash.
This act of blasphemy destroys the social order and plunges the Western World into anomic chaos.
More importantly: Desein (still me) recognises the cash, and as such the cash that is to the other Desein (gangster rapper Obama) ready-to-hand is to me and every other Visa Paywave-reliant Desein present-to-hand, because it has become visible in its lack of functionality, exposing the relational network of functionality assigned to all equipment in this scenario. The spell is broken, and equipment is now obvious rather than ubiquitous.
And the implications for ubiquitous media? Our interaction with the environment comes from an a-priori understanding that we can and do interact with it, in specific ways, for specific reasons, and through specific media. The concept of Desein rests on the assumption that we do what we do without "noticing" - if we notice, then both Desein and design are ruined by being made obvious (present-at-hand), and we are thrown into chaos because we are our functioning-ness.