I am happy to announce the result of 3 months working on the GSoC project: "Communicating with mobile devices". After reading many documentation, thinking about a good abstraction, learning about mobile apps and networks connections, and really valuable recommendations from my mentor, (I really want to thank Michael Snoyman for his availability and kindness) I succeeded in developing 3 libraries to make it easy to send push notifications to mobile devices. They are available on Hackage:
* push-notify-0.1.0.0 : This library offers a simple API for sending notifications through APNS, GCM and MPNS. 
* push-notify-ccs-0.1.0.0 : This library offers an API for sending/receiving notifications through CCS (XMPP - Google Cloud Messaging). 
* push-notify-general-0.1.0.0 : This library offers a general API for sending/receiving notifications, and handling the registration of devices on the server. It provides a general abstraction which can be used to communicate through different services as APNS, GCM, MPNS, hiding as much as possible, the differences between them. 
Now, it is easy to send/receive information with mobile devices, so you can easily develop server applications which interact with them.
So, to clarify this, as part of this project, I developed many test examples, including Android/WPhone and Yesod apps. The code is available on GitHub:  and they are running online on:  , so can be downloaded and tested on mobile devices. (BackAndForth Messaging and Connect4 apps)
Every feedback is welcome!