There is already an option to exclude blog entries by category (great), but I also use hidden pages for certain use.
I know there's an Exclude Posts area under the settings screen, but it would be easier to have this as a checkbox in the post editing screen instead so you can hide it as you create it - especially if you add/remove hidden pages as frequently as I do.
To summarise the request: It would be really useful if there was a checkbox when you create a page or post that, when you uncheck, will exclude that specific page (and any children if present) from the generated sitemap.
For Reference, WP to Twitter plugin does something similar. Excludes categories in the settings, but a checkbox in the post not to ping that page/post out to Twitter.
Hope that all makes sense