A new face recognition ad will only reveal its full contents to women. It uses a "high-definition" camera to scan people's faces, detecting their gender with an apparent 90 percent success rate. The charity, Plan UK, is looking to raise funds to sponsor education for girls living in developing countries; the outdoor display will run the full advert for female viewers, while men will get a brief glimpse followed by directions to the charity's website. It's aiming to demonstrate the limits put on young women in some countries -- and is a pretty admirable use of facial recognition technology. Well, it's not withholding pudding from minors. Check the bus display in action on the streets of London right after the break.