This application is meant to notify you with sound and vibration when the phone asks for a PIN or PUK code to enable the SIM card. This usually happens only when you power on your phone, so what is the reason to develop this tool? Simple, my phone, a new HTC One X, sometimes asks again for the SIM PIN code (maybe a radio bug triggered when there is bad radio signal) and if you don't notice it, you risk to miss calls and messages. It may be useful also if you like to test unstable ROMs which restart without warning.
The app allows you to customize the notification type (ringtone, vibration or both) and frequency, along with other settings.
REMEMBER: launch the app at least once after installation to enable SIM State Locked Notifier. You must do this only once, then it automatically works even after you reboot the phone.
If you find bugs or have suggestions for me, use the feedback function within the app before complaining here on the Google Play market.
DISCLAIMER: This application has been built with HTC One X in mind, and I've tested only on this platform and on Android ICS and Jelly Bean. The SIM state change system notification is vendor-dependant so it may work or not on other phones, just try and test it, and let me know if it works.
ABOUT PERMISSIONS: the android.permission.WAKE_LOCK permission is used to keep the CPU active only when there is an ongoing notification, otherwise the app does not use any CPU at all.