This isn't at all the same, but I think it's in general category of "transition easers": https://mastodon-bridge.herokuapp.com Basically, it shows you which of your Twitter friends have signed up for Mastodon and registered themselves.
It does nothing to share content between the two worlds, but that's probably for the best.
Yep, I knew about that; but appreciate it. Right now, discovery is not my priority...its more about me being lazy to post my stuff to multiple UIs. Its 2017, my lazy self simply wants to post to my gnu social, and have computers under my control auto-post to maybe 1 or 2 other destination silos (coughhttps://indieweb.org/POSSEcough)
It does nothing to share content between the two worlds, but that's probably for the best.