I just posted a couple of ideas in a thread about an iphone app, but it would be relevant to this discussion.
I’m not familiar with the Google Calendar api or anything like that. But, I’m wondering if they have any way of just pulling in a read-only view of the items in Calendar Budget, much the same way you can pull in the holidays into a Google Calendar, or the weather and moon phases into the Google Calendar.
An idea I mentioned in my other post is a text message based entry solution, or a simple form based solution. I believe in Google Calendars you can create links in a custom sidebar, so if Calendar Budget read-only could be pulled in, maybe a link could be set in the sidebar linking you to a simple transaction form.
Overall, a user would still want to log into the Calendar Budget interface at key points in their budget planning, but daily transactions could be posted via the mobile text or form ideas. Then, just preview (read-only, not edit) your Calendar Budget info in other interfaces (whatever you could develop it to work with – maybe RSS?).
Thanks for being open to ideas! Love the Calendar Budget :)