This App needs root. I'm not responsible for any damages. If you point the finger at me for messing up your device, I will laugh at you.
This app allows you to turn on/off the BLN on a Nexus S (crespo). I developed this app because in CyanogenMod 10.1 there was an option to disable BLN. In CyanogenMod 10.2 there is no option to disable BLN. I know that copying the CrespoParts.apk to /system/app will bring back that function but the disadvantage is that you must copy this file after each update. Just install the CrespoBLNConfig.apk and then check the option you want. You have to set this option every time you reboot your phone. An auto-set option will (maybe) come later.
Download: http://bit.ly/CrespoBLNConfig
You can use this source code to learn from it, change things or do some other legal stuff but please mention this repo.