As of 11/20/14, Sprint Direct Connect Now for iPhone is now on the App Store, and even supports iPhone 6/6 Plus.
https://itunes.apple.com/us/app/sprint-direct-connect-now/id889192955?mt=8
https://www.dropbox.com/s/0yo2onadi2wuewj/direct%20connect%20on%20my%20iphone%20account.jpg?dl=0
The Dropbox pic is the options shown on my account and my friends account for Push to Talk.