I don’t think anyone at Realm has ever tried, but I doubt it would work at this point. We do a lot of things specific to each language in the implementation, so we’d have to support RubyMotion explicitly for it work.
RubyMotion is Objective-C under some thin covers so it seems like it would be relatively straightforward to have it work with Realm without a lot of extra trouble.
I'll be following up with this a lot because I would like to cover it on MotionInMotion