iOS messenger SDK

I'm looking to implement an in-app messenger in my current iPhone/androi开发者_StackOverflow中文版d applications. The requirements are that it must be free, real-time, and provide push notifications. I've looked into creating the system myself, but have noticed quite a few apps implement very similar concepts so i figure there must be a drop in SDK/wrapper available.

Here's an example of an app using the of the type of messenger to be implemented:

Like a little: http://itunes.apple.com/us/app/lal-lite-likealittle-lite/id447279762?mt=8

The closest example of an SDK im looking for is something recently released by kik messenger, but they require you to have their app installed (which is a restriction): http://kik.com/dev/

Any other SDKs out there?

First I would like to clarify that you need to chose a protocol before going any further, and this is a multi-part question that requires multiple SDKs / services to implement. Some you can use third party code / services and others you may need to write yourself.

One of the best and most modern protocols is XMPP used by Jabber and Google Talk.

For this there are many libraries out there that are free to use, for Cocoa development on OS X and iOS I use this great library:

http://code.google.com/p/xmppframework/

So far as push notifications go thats a different realm, if you do not want to write your own provider then I suggest you look into a service like Xtify that handles that end for you.

http://xtify.com/ (Free to use)

To build your infrastructure you need to code that yourself from the back-end that makes the calls to your clients. The good news is that if you use something like Xtify it supports both ios and android, and the XMPP library takes a lot of the work off of your hands as well.