So, it appears an app with remarkably similar functionality to my thrice-ill-fated ceekrt has popped up. And they have done it better in every way -- notably, they have snapchat-ified it, meaning that the secrets only show up for a few seconds with no permant (user-facing) records of tweets. Good show! This will pretty much eliminate the need for reporting, and prevent any serious abuse of the system. Now, if only I had thought of that...

Give it a look: Not Secret App

I wish them the best of luck :)