An interesting question. There is really very little research on this and it is difficult research to do as technology changes so fast. For instance, I know of research that shows that use of ‘textspeak’ is associated with better spelling. This research doesn’t speak to the impact of texting on spelling, instead showing a correlation. Also it is now largely redundant as textspeak came and went quickly with reduced cost of texts. We have a PhD student starting later this year who will be looking at apps and literacy learning so watch this space!