“Earth to Echo” is no science-fiction classic, but it serves a purpose for the right, niche audience. The film, directed by Dave Green, is an ode to childhood, and it’s told from the perspective of a young filmmaker named Tuck (Brian “Astro” Bradley) who is chronicling the days before he and his two best friends will be forced to separate. Viewers are supposed to believe the characters shot the film, so it fits into the burgeoning found-footage genre.