Refer to http://forums.gentoo.org/viewtopic-t-926854-highlight-.html

emerge mtpfs
layman -a poly-c
layman -S
emerge sys-fs/jmtpfs

Note media-libs/libmtp should emerge with USE(-crypt).

Then use jmtpfs mount the device:

 jmtpfs -o allow_other  /media/galaxy_nexus/

Note should edit

vim /etc/fuse.conf 

#localhost bin # cat /etc/udev/rules.d/99-android-mtp.rules 
ATTR{idVendor}=="04e8", ACTION=="add",RUN="/usr/local/bin/mount_galaxy_nexus.sh &" 
ATTR{idVendor}=="04e8", ACTION=="remove",RUN="/usr/local/bin/umount_galaxy_nexus.sh &" 

#localhost bin # cat /usr/local/bin/mount_galaxy_nexus.sh 
#!/bin/sh 

echo "Galaxy Nexus connected"
jmtpfs -o allow_other /media/galaxy_nexus
echo "Galaxy Nexus mounted on /media/galaxy_nexus"

</file BASH umount_galaxy_nexus.sh>
#localhost bin # cat /usr/local/bin/umount_galaxy_nexus.sh 
#!/bin/sh 

echo "Galaxy Nexus disconnected"
umount /media/galaxy_nexus
echo "Galaxy Nexus umounted on /media/galaxy_nexus"