The SQL Choice field type allows users to create a dropdown box linked to an external source of data. This can be done using an application definition in the SharePoint business data catalog. However, the business data catalog only comes with SharePoint Enterprise Edition. This product gives your users the ability to connect their sharepoint lists to backend data using SharePoint Standard edition.
The SQL Choice Field Type comes with it's own installer. You can be up and running and connecting to external datasources within minutes of purchasing this product.