The OP previously posted about getting extra pages for his or her US passport, so I will assume the OP is still an American.
You should protect your phone/laptop with a password. If CBP asks you for the password, say no. I've done that. They threatened to seize the phone and laptop but then just let me go.
CBP can turn on and look through any electronic devices at the border, for any reason, or for no reason at all. But if you land at LAX and they want to seize your password-protected phone to de-encrypt it, they need "reasonable suspicion" that you're a criminal.
http://www.politico.com/blogs/under-...tronics-158891