CiviCRM SMS integration is a powerful feature. However, with many people moving to use instant messaging services like WhatsApp, has there been any move to integrate CiviCRM with and instant messenger, in particular, WhatsApp? Out organization has recently moved its bulk SMS database over to WhatsApp, as 90% of our members use WhatsApp. Being a non-profit, we gain from not having to pay for sending bulk SMS's.
They haven't been any to my knowledge, but assuming whatsapp as an api to post messages, it shouldn't be too complicated to implement.
If you are interested, you could write an extension and use the searchtask hook to add a "send via whatsapp" action http://wiki.civicrm.org/confluence/display/CRMDOC/hook_civicrm_searchTasks
Regarding whatsapp I have been looking into that recently and I discovered that WhatsApp doesn't offer an API. So it is not possible to send or receive messages to/from whatsapp in CiviCRM.
However it is possible to hack around this. You could create your own android app for sending whatsapp messages and then you run this app on your phone and this app talks to whats app on your phone. And CiviCRM talks to this app. This is how it might work however it is against the policy of whats app. So there is a risk that your whats app account might be blocked.
Free messaging services are popular with spammers for obvious reasons, and WhatsApp will be doing their utmost to avoid their service being used in a way that doesn't suit their profile.
I predict that any bulk WhatsApp integration implemented can anticipate a game of "cat and mouse" with the WhatsApp developers. If pursuing that path, budget accordingly - paid SMS may not be so expensive after all.
If WhatsApp decide in future to allow promoted messages, they'll price it accordingly. The lack of bulk messaging in the platform (notwithstanding infrequent abuse attempts & hasty shutdown) is a feature to them.