More general question would be: how to use "Custome Property Types"

We are using approach below:

[EditorDescriptorRegistration(TargetType = typeof(string), UIHint = "ListOfChoices")]
public class ListOfChoicesEditorDescriptor : EditorDescriptor
{
    public override void ModifyMetadata(ExtendedMetadata metadata, IEnumerable<Attribute> attributes)
    {
        SelectionFactoryType = typeof(ListOfChoicesFactory);
        ClientEditingClass = "epi-cms.contentediting.editors.CheckBoxListEditor";
        base.ModifyMetadata(metadata, attributes);
    }
}

public class ListOfChoicesFactory: ISelectionFactory
{
    public IEnumerable<ISelectItem> GetSelections(ExtendedMetadata metadata)
    {
        var options = new List<SelectItem>
            {
                    new SelectItem { Value = "value", Text = "text" }
            };

        return options;
    }
}  

And then in page type:

[Display(GroupName = SystemTabNames.Content, Order = 20)]
[UIHint("ListOfChoices")]
public virtual string Choices { get; set; }

@Valdis, I have tried and I get 404 from http://localhost/secureUI/Shell/1.0.456/ClientResources/dtk/epi-cms/contentediting/editors/CheckBoxListEditor.js

any idea?

Interesting mine is coming from "{secureUI}/CMS/2.1.82/ClientResources/EPi/Cms/contentediting/editors/CheckBoxListEditor.js"

The client widgets changed root namespace in the 7.2 UI upgrade. For 7.1 the namespace should start with "epi.cms" and for 7.2 "epi-cms".

Indeed Linus :) It helped.