Mouthwash brand Listerine has developed a smartphone app that helps blind people to "feel" when people are smiling, using facial recognition technology.

The Johnson & Johnson-owned brand worked with JWT London on the app, which is available to download on Google Play for Android devices. Using the phone's camera, it can detect a smile up to five metres away and notifies the user with audio (a beep) or with vibration feedback.

JWT also created an emotive short film to promote it, showing how it feels for blind people to know when someone is smiling. Directed by Oscar-nominated documentary maker, Lucy Walker, whose films include "Blindsight" -- a documentary about a blind mountaineer leading six blind children up a mountain --it features interviews with four blind people who explain what the app means to them. Their different reactions are clearly authentic (such as the woman who says she'd love to take this app on the Tube, to see if anyone actually smiles) and it does an excellent job of explaining why the app could be important, and indeed more than just a brand gimmick.

The app and campaign are launching in the U.K., Ireland, South Africa, the Netherlands and Germany this week, supporting the launch of Listerine Advanced White mouthwash.