Hi Moe!
The main requirement for a sandbox URL is that it actually is resolvable/can be contacted from your browser. If the URL above loads your app locally, that should work for the redirect URL.
You are correct that the launch URL is optional and wouldn't be needed for a standalone application.
You can post in our
google group if you have any additional questions about Cerner's sandbox, tutorial, or documentation.
Regards,
Jenni