Jott has just added a new feature which allows you to update Twitter by jotting. Jotting is the process in which you call a tool free number (US only) and use speech recognition commands to complete a task.
To send a tweet your voice is recorded then processed by Jott's speech to text interpreter. Then it sends a tweet to your Twitter account. I tried it out last night and it worked quite well. The only downfall is there is no 1-800 number for Canada. In order for it to work you must call a Toronto area number so long distance fees do apply.