I've been wondering about this.... Link to a blog post announcing some research: Investigating the Potential for Miscommunication Using Emoji "Hey emoji users: Did you know that when you send your friend on your Nexus, they might see on their iPhone? And it’s not just ; this type of thing can happen for all emoji (yes, even ). In a paper (download) that will be officially published at AAAI ICWSM in May, we show that this problem can cause people to misinterpret the emotion and the meaning of emoji-based communication, in some cases quite significantly. , we know."
Say it isn't so!!! Actually, lately I've been doing screen captures (cropped) and sending those. I search the web for pictures of related sentiment, crop the image and then send that in text (MMS).
Yes, as a developer I've seen that the emoji is not guaranteed to come across between platforms. I think some of the emoji may even change between versions of the OS, at least on Android.