(CNN) The website Runpee.com has been around for more than a decade, advising movie-goers about the best time -- should nature call -- to run out for a bathroom break. Still, with this weekend's release of the three-hour-plus "Avengers: Endgame," the site/app might be ready for its closeup.

"This is as big a movie as we've ever done for Runpee ," Dan Gardner, the app's founder, told CNN, adding that the app has just over 100,000 registered users.

Notably, it was another three-hour movie, Peter Jackson's 2005 remake of "King Kong," which gave Gardner the idea for the site. As he tells it, he needed to go but didn't want to exit the theater, lest he miss a key scene.

Within a few years, that seed blossomed into an actual website/app, one that provides cues regarding when to leave without missing anything that's fundamental to the plot or story. It is, of course, a somewhat subjective measure, which explains why the site also solicits feedback from film patrons.

If that sounds simple enough, it's actually a bit more complicated, since Runpee usually offers more than one cue for each movie, and endeavors to word them so that they don't contain spoilers. The app also provides information, should someone step out, about what they missed, approximating the role that a friend (who has the bad habit of talking during movies) would play.

Read More