The app is still in its beta version and is available on Android devices, however, you can download it and file your complaints now.
It's fairly easy to use; download it and then sign up via Facebook or Gmail account. You create a user account, and then you have options like complaints and SOS.
Within complaints, you can choose to register your complaints under auto/taxi and choose a category like "over charging", "over speeding" etc.
The idea is to create a system wherein anyone can register their complaint, and get an answer within a certain period of time. You can also log back in, and check the complaints that have been filed by you along with its status.