Several but it really depends on what you are actually trying to achieve.
Also, do you know how the phone shows itself as a USB device?
You can use one of the PIC24 or dsPIC33 devices that have an OTG USB peripheral which can act as a USB host.
Or you can buy a separate USB host device and communicate with that via UART/SPI/I2C/whatever it uses.
Susan
"Technically" it can be done. Android is based on Linux so u have to customize linux.
Customize linux so it can take data from PIC(PIC MCu must also communicate via USB protocol)
and then send these data to the mobile GSM modem.
So technically possible. For an expert it will take a year or half to complete this..!!
For a newie impossible.!!