Unlocking the Bootloader on your Android device allows for all kinds of modifications. Not only does it allow for custom recovery, roms, and kernels it also makes the process of developing these customizations much easier for those that develop. Unlocking the Bootloader on Nexus devices is very simple. You just go into fastboot mode and type "fastboot oem unlock" in a command prompt, and you are done. This is easy enough but the downfall is that Google's method requires you to wipe data as a security measure. Developer "Segv11" has created an APP that allows you to Unlock the bootloader without fastboot. This app has been developed so you can relock and unlock the bootloader on the fly. With your bootloader relocked it will be more secure since no one can install a custom recovery to your device, but this allows you the flexibility of easily unlocking the bootloader as well.
Via XDA