At any institution of higher learning there will be a teacher whose lectures are boring. It's not hard to tell when students are bored—they're usually staring off into space, texting, or sleeping. But some teachers may have lost this ability, having become habituated to a lack of eye contact, and Bill Gates is going to help teachers measure students' boredom with galvanic response bracelets.
Skin conductance is basically a form of electrodermal activity which will grow higher in number whenever one enters a state like excitement, attention or anxiety, and the activity will actually drop during states such as boredom or relaxation. Researchers at Clemson University have already received some dough from the Gates Foundation to look into the matter deeper, where the feasibility and utility of using such devices regularly in schools with students and teachers should be presented. The amount is not small–$498,055 to be exact, and if it can help increase the efficiency as well as effectiveness in the classroom around the US, then it is definitely something worth developing further.
Videogame applications of the same technology could ratchet up the difficulty if you're too calm or relaxed, too. But measuring levels of excitement doesn't mean we have to make everything exciting; the same technology can help anxious students know when they've physically relaxed. There's already a game for that.