Integrating separate apps into one Rails App

I have built multiple Rails Applications that handle the various services I run, e.g. Mail, DNS, Radius etc.

I want to bring all those apps together under one umbrella to have a centralised login system so that I can start working on user permissions, i.e. each user can login and view/change the information that relates to him as well as look at graphs and such.

My end goal is if we deploy a service, to build the service separately, and then drop it into the main system, adding menu items as need be.

Is the best way to do this using components or plugins?

Regards,

-John