Most viral videos have a very short half-life, but occasionally they have a much greater impact than you might imagine.The founders of OneCourt, Field of Vision and Touch2See—based in Seattle, Dublin, and Toulouse respectively—weren’t all inspired by exactly the same clip, but the videos they did see were all variations on the same basic theme: a blind person having their hands guided by a companion across a facsimile of a soccer pitch in order to better understand what was happening in a live g...