new

 <%= form_for @time_tracker, :url => {:action => :stop},
                       :html => {:class => "time-tracker-form",
                                 :onchange => "<my-suoer-prototype-request>",
                                         #:update => {:success => :nothing, :failure => "time-tracker-control"},
                                         :url => {:controller => :time_trackers, :action => "update", :format => :json},
                                         :method => :put,
                                         :with => " Form.serializeElements( $(this).getInputs() ) ")} do |f| %>
              <!-- TODO localize placeholders / add labels -->
              <%= f.label l(:time_tracker_label_current_task) %>

old

 <%= form_for @time_tracker, :url => {:action => :stop},
                       :html => {:class => "time-tracker-form",
                                 :onchange => remote_function(
                                         :complete => "function(response) { alert('response.responseJson') }",
                                         #:update => {:success => :nothing, :failure => "time-tracker-control"},
                                         :url => {:controller => :time_trackers, :action => "update", :format => :json},
                                         :method => :put,
                                         :with => " Form.serializeElements( $(this).getInputs() ) ")} do |f| %>
              <!-- TODO localize placeholders / add labels -->
              <%= f.label l(:time_tracker_label_current_task) %>