A Google AdWords API thread reports that Google is in the process of working on a "simple application that will allow you to visually browse the contents of your AdWords sandbox accounts." The purpose behind this is to enable developers to see the types of requests, number of requests and so on being made by their applications. This can help developers visualize the cost and impact of their apps.
Eric Koleda from the Google AdWords API Team said in response to the question about this:
We are working on releasing a simple application that will allow you to visually browse the contents of your AdWords sandbox accounts. There is no version of the AdWords web interface however that will work with a sandbox account.
This can be great news for the AdWords developer community.
Speaking about the AdWords API, version 13 is being sunsetted in about a week, so make sure to upgrade to V200909 before April 22nd!
Forum discussion at Google AdWords API.