how to unlock? simply replace the sim card on your usb modem such as globe tattoo, smart, sun dongles and it will auctomatically detect a change on it and ask for you the unlock codes. you have a limit of 10 tries and its screwed. unlocking the codes needs the IMEI number and model. i couldnt find a tool to generate it but, a lot of people offers to unlock the codes for you. others make money in exchange for the code.
once you have the code just type it in, then make a new profile with empty settings with just the default data only. then connect with the operator of your choice and voila you got yourself a mobile internet access.
why would you need to open-line your usb modem? its because if you do some traveling and needed some access on the field, and you are locked to just one carrier. signal depends on location so you just easily switch to a different carrier that has a good signal in that area you are in. so that you can maximize the speed and save money of buying another modem from another carrier. http://yellowbars.blogspot.com/2009/10/globe-tattoo-unlocked.html
SUN & Globe uses the HUAWEI E160 and it has a connection on side for an external antenna which is nice. You can get unlocked at http://www.sulit.com.ph/ just type SUN unlock and you will get the instructions how to load the sign it details for SUN, SMART or Globe after it is unlocked. I have tested the service and it works.
Learn more about unlocking here