I am using SharePoint Online and I have followed the steps of the tutorial:
But the OData service url was the list of the second site collection.
https://myTenant.sharepoint.com/sites/Site Collection 2/_vti_bin/listdata.svc/
And I am getting the forbidden error, once the app initializes.
Another way I have tried was by uploading the ect file generated on Visual Studio and follow the tutorial in http://www.sharepointconsultant.ch/2013/11/09/consuming-an-external-odata-service-from-an-sharepoint-2013-app/
The difference is that I didn't find a way of making the step 11 on SharePoint Powershell, but I did it using the UI. But in anyway it didn't work.
I am getting the forbidden message as well.