I was expecting a service that would scrape all the G+ profiles for the twitter names listed there and compare it with my list of twitter followers.
Hard to categorize a tool as useful if it has social network effects (needs critical mass).
Note that by signing up you're giving up the profile association willingly into their database.
I've actually started making posts that say, "If you can see this post, I'm following you because [X]."
- firstname.lastname@gmail.com - https://plus.google.com/100033678853935069816 - 100033678853935069816
??
It relies on people you follow having used http://gplus.to to create a Google+ name that matches their Twitter name.
Currently it finds about 20% of the people you follow.