It's old news but I've just come across it.
This has been linked from here (in french):
This bluetooth earplug is to be attached on your index finger.
Then you put your finger in your ear when your receive or make a call.
The device will send vibrations through your fingers' bones.
Then the ear will transform the vibration in sounds.
To talk you just speak softly and the device will detect the vibrations.
The device is particularly suited to busy and noisy environments.
The article in french also mentions that it works when you put your finger in your nose ;-)
I can't help but imagine all the fun people can have with that.
Imagine 2 guys, Remi and Zac, in the street.
Remi (receiving a call): Hi Jen, how are you?... good ... you want to talk to Zac? ... hold on a sec, I'm putting my finger in his nose