Thank you for your post.
At this time, FileMaker Go (nor FileMaker Pro) has a script step or button that will invoke the Dictation feature of the new iPad. I recommend entering this suggestion into our Feature Requests web form at:
The entries into this web form are automatically entered into a database file that is hosted by Development and Product Management, where they are then discussed and considered for future releases. Although I could copy your post and paste it into the web form, there are a couple of questions asked that only you can answer.