I have, over the years, made several products with password. You will need two things:
1) a 'service password' that is NEVER communicated to anyone - if it has to be keyed in = billed as a service call.
2) the ability for the user to change the password.

I have, on the request of sales or management made systems without the two and in all those cases had to add them. Without #1 you have to reprogram the chip when the user forget the password he entered and #2 because there is always "we do not want Joe to know the password any more"

Erik