I'm working on a side project and the setup is basically that you get to see all the data I have on you. Granted this is a tiny project that is largely just for me, but as a policy that seems like that is the most clear cut way to go.
Yeah kind of cool. I believe tools like that came from either mass opt-out tools by the Network Advertising Initiative or the Digital Advertising Alliance.
They accomplish what they intend to do, its just that most users want them to do more.
If you use that tool on all of your devices (and don't clear your cookies/etc) you will be opted out of those vendors tracking. But that doesn't accomplish since that type of targeting only makes up maybe 15% of targeted advertising. All that tool does is get you shittier ads. (Oracle's just shows you what data they know about you, it doesn't actually delete or opt you out).