Child-proofing an Android phone?
Activate Fixed Dialing Numbers feature from Call Settings (and, add numbers there to allow). You may need to contact your carrier. This is supported by even classic Nokia phones, so all ROMs should support it.
Kiosk lockdown the device and allow only Phone/Dialer app in Kiosk Mode. For Kiosk Mode, try searching "Kiosk" in Play Store. SureLock Kiosk Lockdown app looks great to me.


Don't forget to allow kid apps other than phone in Kiosk Mode. Happy Parenting!