Citrix Podio is a platform for developing applications which can be used on the web or mobile devices. People can build business applications by simply drag and droping fields to create forms and views. It requires very little development knowledge and no actual programming language skills.
Then have recently added a feature I asked for, which allows you to limit the choices that are displayed in drop down lists.
While I like the addition, you still have to create a view for each filtered value that you want to use in lookups. I'd prefer to see a formula like @ApplicationLookup("AppName","ViewName","FieldValue")