Many moons ago, when I was but a humble research student, there was a research group at Huddersfield University looking into earprints as a forensic tool.
Obviously that research has borne fruit, although it looks to have taken the best part of twenty years.
The BBC reports that Yahoo tests ear-based smartphone identification system.
There is still some debate over the validity of earprints in a court of law, but I suspect smartphone unlocking is probably held to slightly less stringent standards.
For the really interested, here's a preprint.
[Image credit: one deep drawer]