If the mobile phone is stolen, change it to a mobile phone that will automatically send text messages to inform you.

This is not the function of mobile phone, but the function of software, which is available on symbian and smart phone. For example, the phone used by UIQ is called phonesecure. After setting the mobile phone number, as long as the mobile phone card is changed and turned on, it will secretly send a text message to the set number. So whoever steals a mobile phone has nothing to hide. My mobile phone was found twice, haha.