Motorola has been doing this with devices, even pre-cell phone revolution.
Look at their old pager lines - i.e. the Pronto, Bravo, etc. They used to let providers "lock down" the pager with a programming PIN. Want to change the capcode? You need the PIN. Put the PIN in too many times, and you have to replace the code plug, which meant factory service. (Essentially, you had a dead pager.)
See here: http://www.qsl.net/kb9mwr/projects/pager/pagerpw.txt