I want a MarsEdit style bookmarklet-driven editing application for Twitter.
(MarsEdit lets you bookmark and compose blog posts on your system, even while you are offline. You can write a bunch on the plane and upload them later, for example.)
It should:
- abbreviate and include page/asset link
- track character count during edit
- save drafts locally for posting later
- support upload of assets (ie pics to twitpic)
- sync with Twitter to keep a database of all my tweets and drafts
- import my @replies, dms & the results of some preset Twitter searches
- drafts and tweets should be searchable
- offer versatile publishing tools to repurpose tweets and replies for blog posts, etc.
I get that I am among relatively few people who would really use this tool, but that could change. Maybe MarsEdit itself can just add (some of) this as a feature?
formerly posterous... 
A few additional features I think you’d need in order for an offline Twitter app to work:1. If you had a particularly long flight (or period offline, whatever), you might also want to specify a delay between the posting of each draft tweet out of your MarsEdit "outbox" to avoid having all tweets written offline from being uploaded simultaneously when you come back online. This would allow a more "normal" interval.2. A related nice-to-have feature would be the ability to arrange the order of draft tweets in the outgoing queue. The first tweet you write while offline might not be the one you want to go out first.3. Finally, it would need to accept links offline. This is problematic since the length of the link counts against your total 140 character limit. Therefore, MarsEdit would need to know at minimum what the length of the compressed URL is prior to going online to retrieve the actual compressed URL to be dropped into the tweet. I don’t know if the length of these compressed URLs is dynamic (at least an examination of several tinyurls makes it look as though they are all six extra characters wheras snurls are five, but that’s from a very small sample).
Blogo might fit the bill. http://www.drinkbrainjuice.com/blogo
Whoops, looks like Blogo won’t do offline posting. Rrgh.For my part, when I want to offline-tweet I usually just use Twittermail. You can postdate tweets with it, although it involves a bit of mental timezone arithmetic. Perhaps a very small script that would take the tweet and the desired time and format the email…