VidaTak makes EZ boards (low tech) in many languages, including chinese, and they have an iPad app called VidaTalk that can be purchased for $89.99 in the app store that is Chinese.  I contacted the company about Mandarin vs Cantonese, and I was told that both the EZ board and the app are in Simplified Chinese. 

According to a couple of different websites, Simplified Chinese was introduced in the 1950s in the People’s Republic of China as part of language reforms to increase literacy. As the name suggests, it’s a simplified version of Traditional Chinese: the reforms decreased the number of strokes by an average of one half and simplified the forms of a sizable proportion of traditional Chinese characters. This simplified character set appears in all print media in Mainland China and Singapore. Over time, the two language versions have also diverged in terms of vocabulary and grammar. Modern terms such as ‘software’ or ‘network’ have different translations in Simplified Chinese (SCH) and Traditional Chinese (TCH) respectively.

I think it's important to note that Simplified Chinese is a written language rather than a spoken one.  Makes you wonder what the text-to-speech will come up with?  I did check the keyboard options in the iPad, Simplified Chinese is a keyboard option.