I use iThoughts (the mind mapping app) on my IOS devices as a translator between my FT documents (saved as .md not the FT native format) and OPML which can then be opened in OmniOutliner or something like CarbonFin Outliner (which as a great alternative if you’re looking for a cheaper IOS outling alternative).
FT documents saved in .md format function in exactly the same manner as native FT docs, the only disadvantage is that FT specific modes such as timer and todo won’t function with documents saved as .md
However if you mainly use FT as an outliner that takes advantage of Markdown formatting, this is a really fluid solution. The really great thing is that iThoughts also creates faultless translations when transitioning from OPML back to Markdown.
FoldingText on OS X partnered by iThoughts, Editorial and OmniOutliner on IOS makes for an incredibly powerful productivity combination (with everything remaining in perfect sync via Dropbox).
It’s worth saying too that iThoughts is a superb mind mapping app in it’s own right but if you only ever use it for format translations it’s still incredible value for money.