I have good experience for Zebpay since 2 years and this is the best wallet in india and there is no issue with it.
Concept - Zebpay provide exchange of bitcoins between users and easy way of trading of bitcoins and hold in wallet.It also hold bitcoin cash.
Layout & Design - It has easy interface and fast processing app.
Feature -Transfer from Zebpay to Zebpay free and third party has 300 bits charge and network fee is 0.0005 BTC. Buy bitcoin is free and sell is with 100 Rs. deduction.
Usefulness - This is the best app I recommend to install and easy to trade in Bitcoins.