body-language
Explanation
The Joke
A person complains that texting is bad because it doesn't capture body language. In response, another person (a red-haired tech enthusiast) announces that he's made an app that captures the expression on your mouth and the inclination of your body, combining them with your words. When the first person tries it out, the app shows a crudely drawn face saying "Do you like my new app?" and the response is simply "yes" with a deadpan stick-figure expression. The app faithfully captures body language -- which in this case reveals the user's total lack of enthusiasm.
The Humor
The joke operates on two levels. First, there's the irony that people who complain about texting lacking body language probably don't realize that their own body language would often undermine their words -- in this case, the flatly unenthusiastic "yes" paired with a bored expression reveals that the person doesn't actually like the app. Second, it satirizes the tech-solutionist mindset: someone heard a complaint and immediately built an app to solve it, only for the "solution" to make social interactions more awkward rather than better. The body language that texting mercifully hides turns out to be something people might prefer to keep hidden.