A communication of a web app with others is not a surprise, but it is the demand of mobile world's era. Because new apps want to maintain a centralized DB which could be shared with other apps very easily and very frequently. Recently, I also worked on a similar distributed web app which provided me an idea to implement a rubygem.
ActiveResource is a ruby library which acts same as ActiveRecord, but perform operations over API. ActiveResourceAssociatable is also a ruby library which consolidates same kind of associations methods as ActiveRecord provides. However it could be achieved by own customized methods, but ActiveResourceAssociatable provides smarter way of accessing your ActiveRecord and ActiveResource methods. ActiveResourceAssociatable comes with some options too which will make you more easy to use this gem.