Don't worry about optical eavesdropping just yet. The experiment only got accurate reproduction with specialized cameras that shoot at up to 6,000 frames per second; an off-the-shelf device with 60fps recording can identify people's voices, but it's hard to make out words. Provided the technology reaches fruition, it would most likely be used by investigators that want to hear what suspects say when they're not on the phone. It would be useful for more than surveillance, too, as team member Abe Davis believes the visual mic could identify a material's properties without making contact. It's definitely clever tech -- let's just hope that it's used more for science than snooping.