Re-programming PIC microcontrollers with USB through smartphone
Whether or not you need USB OTG depends on the capabilities of your phone.  If your phone cannot act as the USB host, you will need the microcontroller to act as the USB host.

There are many PIC devices that have USB hardware (and USB OTG) and can be self-programmed.  You may need to be more specific about your needs if you want recommendations for particular microcontrollers.