Bluetooth and RaspberryPi:
Fortunately, a lot of Bluetooth USB keys are supported by the Raspbian linux distribution. Some Goggling and you find how to install it:
It starts with the installs :
sudo apt-get install bluetooth bluez obexpushd
Followed by the config.
sudo hciconfig hci0 name "my_funny_name"
This is to change the name seen by the other devices when scanning.
sudo hciconfig hci0 piscan
This is to make it discover-able
sudo bluetooth-agent -c NoInputNoOutput 1234
This is to make it pair-able with the code "1234" and with no confirmation on the raspberry side. (I found it's quite hard to find information on bluetooth-agent command line option...)
sudo obexpushd -B -o /home/pi/project/piprint/
And finally start the file server, which auto accept file and save them in the specified folder.
To make it each time after boot, I edited the /etc/rc.local file. By adding these lines:
sudo bluetooth-agent -c NoInputNoOutput 1111 &
sudo hciconfig hci0 piscan &
sudo obexpushd -B -o /home/pi/project/piprint/ &
sudo java -classpath .:/home/pi/project/piprint/lib/'*' piprint.Launcher
Last lines are to launch the printer program, that I'll describe a bit later.