There was some research after the Vietnam war to provide blind veterans with a device on their back that used a matrix of 'pins' to 'draw' the output of a video

There was some research after the Vietnam war to provide blind veterans with a device on their back that used a matrix of 'pins' to 'draw' the output of a video camera on the users back.. Supposedly, it worked quite well - wearers got VERY good navigating with it and seemed to like the tech overall. Not sure why it disappeared - cost (it was probably made from pretty pricey tech for the time)? Weight ? battery life ?