This is the answer to my question of a while back:

Q: Can I post to my TypePad site using a desktop client using XML-RPC? A: Yes, TypePad supports both the blogger and metaWeblog XMl-RPC APIs, along with the extensions supported by Movable Type. You should be able to use any desktop clients that you’ve used with other weblogging tools. For example: Kung-Log; NetNewsWire; Zempt; w.bloggar. If your tool supports RSD (“Really Simple Discoverability”), you can simply enter your weblog URL, and your TypePad username and password. If your tool does not support RSD, you should use the following XML-RPC endpoint:

So in short: yes I’ll be able to post to TypePad from an "off-line" client. Nnnnice! Come to think of it, I should be able to post to TypePad from Radio… I’m off to try that.