The computer voting machines in my county already show you a crystal-clear summary page before the vote is finalized. If you leave something blank, a large red marker on the screen shows this. You can still leave it blank if you want, but it's damn hard to do it by accident. I have never seen anything more idiot-proof in my life.

As for the rest, the simplest solution is to have the computerized voting machine print out either a punch-card, or preferably, a black-mark machine-readable ballot (not a bar code, but something that can easily be read manually), and the voter simply checks it to make sure it says what he wants it to. If he likes it, he can drop that into a conventional locked ballot box. If not, the machine can be reset to try again.

If the election is not contested, the printed ballots go into secure storage just like regular paper ballots. If there's a problem, recounts can be accomplished either by standard optical scanners or by manual count.

Technologically, this involves the equivalent of plugging a printer into a computer. I can't figure out why everyone is trying to make such a big hairy deal out of it.