Restful routes for ajax?

I'm looking for examples using resource-base, aka restful, routes for
ajax requests. So far, I've resorted to adding routes for ajax with
explicit

  map.connect ':controller/update_ui/:id', :action => 'update_ui'

Presumably, the same could be done with something like

  map.resources :mymodels, :member => { :update_ui => :get }

The problem I've encountered there is that it breaks down when I try to
use it from a view that shows a new object and thus doesn't have an id.

Michael