Siskin IM by Tigase, Inc. is a lightweight and powerful XMPP client for iPhone and iPad.
Siskin IM is easy to use and lightweight XMPP client. It has support for file and image sharing, group chats, end-to-end encryption and many more.
After installation of Siskin IM it will suggest you to add or register the XMPP account, which you should do. After that you can start chatting with your friends using your XMPP account.