Probably not the greatest of poll measures, but BBC News 24 has a show called Question Time Extra which discusses the show on BBC 1 and talks about the SMS text comments.
This evening's Question Time was, obviously, dominated by MPs expenses. Interestingly they normally receive around 2000 or so text messages. Tonight it was over 5000. The producers also said it was the angriest they've ever seen.
My guess is, as this saga rolls on, it will not be long before we finally have a by-election somewhere.
Postscript: I see Shahid Malik has said he claimed within the rules and won't be paying anything back. I give him a couple of days before a U-turn or a resignation.