Python script to create Android/iOS strings from a .csv
The Python style for naming is snake_case for functions and variables, and PascalCase for classes. If you have constant variables (values don't change), they should be in UPPER_SNAKE_CASE.

You also shouldn't be importing multiple modules on one line, like you've done here:

import sys, os, getopt, csv, xml.etree.ElementTree as ET


These imports should be separated onto separate lines, as per PEP8, Python's official style guide.

These comments at the very top of your file:

# Script takes a csv and creates strings for Android (.xml) and iOS (.Strings).
# csv in the format [key, language1, langauge2 ......]
# usage - Python converter.py [FILEPATH]


Should be converted into a docstring, like this:

"""
Script takes a csv and creates strings for Android (.xml) and iOS (.Strings).
csv in the format [key, language1, langauge2 ......]
usage - Python converter.py [FILEPATH]
"""


This is not how you should be opening files.

f = open('Strings.csv')


Rather, you should use a with ... as ... context manager. By using a context manager, you can ensure that the file is properly closed. Here's how you'd do that:

with open("Strings.csv") as f:
    ...


Finally, the below line does nothing.

++rowIndex


It should be changed to row_index += 1, if I understand your intent correctly.