I'd just like to see a voice interface that has any attempt at natural error correction.

We do this in a hundred ways in English, emphasis, meta-words, too many to fold into a system. But with a little user prodding, I think you could cover enough of this ground to still sound almost natural.

  Asst.: Would you like me to read that back to you?
  User: Yes
  A: The click brown ox...
  U: The _quick_ brown _fox_...
  A: Ok. The the quick brown fox jumped over the lazy log. 
  Is that correct?
  U: No.
  A: Which part [is incorrect]?
  U: The the quick
  A: The the quick. What should it be?
  U: The quick.
  A: The quick brown fox jumped over the lazy log. Is that 
  correct?
  U: No. Lazy dog.
  A: Lazy log?
  U: No. Lazy dog.
  A: Spell "log." <Or "Spell" + recording of user's voice saying ambiguous word>
  U: D-O-G.
  A: Ah. The quick brown fox jumped over the lazy dog. Do 
  I have it now?
  U: Yes.
  A: Say 'send' to send message.

Agreed that voice systems are an incredibly hard problem, but I suspect rule-based natural language correction systems would go a long way.