I want to develop custom lock screen app that looks like iPhone's lock screen.
Are there are any tutorials or examples for this? If not, where should I start?
There is no support for creating a "custom lock screen aap" in the Android SDK. You can only modify the lock screen behavior in custom firmware.
UPDATE
Note that Android 4.2 does allow you to create app widgets that can be added to the device's lockscreen, which may meet your needs.