Yes, the existing Clickatell plugin works great. I might be interested in getting 2-way SMS through Clickatell but need to check coverage in my region first (Scandinavia). Last time I check it wasn´t supported. Are other developers interested, I will look into it.
I am still interested in Twillio or any other provider that can integrate phone capabilities, IVR (and video calls as well) etc. etc. in Aware IM and Twillio is great, especially if it has been done, tested and proved to work well (Himanshu can hopefully chip in with comments about this when/if he sees this post). I would be interested in looking into a REST integration with Twillio so if other developers are interested, please comment here.
PS: Whatsapp integration would be incredible as well, I didn´t even know that was possible?