Yes, This tool is using the Google API to do the transliteration. What is unique about this tool is that it also lets you convert any existing Roman Urdu on the web-page to the corresponding Unicode Urdu characters. Again, it uses internally the Google API for these, but I haven’t found any other tool on the web which does this.
It means now you can convert the existing shairy, ghazal, blogs written in roman urdu to actual urdu characters. I found it very helpful in the reading.