One of the most annoying things ever - backup and restore all of your data while the bootloader is unlocked. Is there any way to avoid getting the data wiped? Answer is, as you might expect, Yes, it is possible with this little handy tool called BootUnlocker.
If you ever tried to root your phone the classic way with unlocking your bootloader, you surely know the command "fastboot oem unlock". This command, however, wipes all of your data.
So even if your phone is rooted and you wish to unlock your bootloader, you have to backup all of your data first and restore them afterwards the bootloader is unlocked.
Bad thing is, your device has to be rooted to unlock without wipe and it's currently supported for Nexus devices only (without Nexus 7), that means: Nexus 4, Nexus 5, Galaxy Nexus and Nexus 10.
BootUnlocker, however, doesn't require an USB connection and the device won't even reboot. It's just that fast and simple. App is available for free on Google Play store.