Let me propose an idea.....
I was going through old issues of phrack, and I found this
http://www.phrack.org/issues.html?issue=50&id=9#article article which was the plans for a gold box, which is pretty much a diverter. The author claims it works in SS7, and it only costs $7 to make.
So, how about this. You hook it up to two lines (the box requires two lines, but only one has to be to a number you can red box to) that aren't owned by anyone (I'm not sure where, suggestions needed) that you can redbox to from your favorite payphone. Then, essentially, the payphone turns into an anonymous and free phone.
But there are some things I'm unsure of. Does the box even work? I haven't tried it yet of course, I don't think I could make it if I tried. Also, where would you hook it up where it would stay? I'm not sure how long it would last in a can, and it sure as hell couldn't be hooked up to a residential line.
Anyhoo, feedback would be really appreciated. And I posted this here instead of on the binrev forums. You should feel very privileged. One more thing - could someone convert the text of the picture of the diagram into a gif? I have no idea how to do that.