Russell Beattie's Moblogger is a client-side Java application that grabs email messages sent to a special account and posts them to your weblog (as long as it supports the Blogger API which most do). He also handles media attachments (pictures, sound, video), which opens up cool possibilities if you have a multi-media phone that can send e-mail.
I think he's on the right track here because this uses standard e-mail which most (if not all) mobile devices can support. Rather than creating weblog-type client apps for various devices, just do everything through e-mail.
I'd like to take it a step further and create a server-based system that you could register with, then send email directly to a special location. The server would then update your weblog and reply back to you with a confirmation message.
