In order to install the application, you must have a S60 3rd or 2nd edition phone. Check the list here. 

Then you must install Python for S60 on your phone. Download it from here.

Finally you can download the application package and unzip it to your Python folder on the SD card of your phone. If you don't have a folder named Python, you must create one.

Run Python, click options > run script > e:invisibles.py 

Enjoy!

This code is available for non-commercial purposes. Don't use it for commercial applications without contacting the author for permission.