[O] enhancements for org-agenda-to-appt

[Peter Münster]

Hello,

Before enhancing org-agenda-to-appt (and some other parts) to fit my
needs, I would like to get some feedback for my ideas:
- General opinions about the ideas.
- Hints about already existing usable code.
- Hints how to implement the ideas with the least effort.

The general idea is, to get notified when a task has to be done, without
any need to open the agenda. Default settings for the notifications can
be overwritten for each task (by settings in the timestamp and/or
additional properties).

Here the details, in the order of priority:

 1.) Warning period should be taken from timestamp
     That means, that the warntime must be passed to appt-add.

 2.) Warning period in hours and minutes
     "-3h" for 3 hours or "-10M" for 10 minutes should be possible.

 3.) Notification must continue when timestamp is past
     Perhaps, the notification should be even more aggressive, when a task
     is overdue.

 4.) Easy modification of timestamps
     Often I get notified, that a task has to be done now, but the most
     obvious and easiest solution for me is: just do it tomorrow!
     Thus, when point is on a deadline line, M-right should advance the
     time by 1d, C-right by 1h, or similar.
     Decrementing with M-left and C-left should be possible too, but will
     surely be used less often... ;)

 5.) org-check-deadlines must consider hours and minutes
     It should be possible, to show only overdue deadlines, even if they
     are overdue since 5 minutes.

 6.) Timestamps with hours and minutes
     When adding deadlines or schedules, there should be also the time,
     not only the date.

 7.) Switch from "todo" to "done" by clicking on the notification window
     When using `notifications-notify' this should be possible with the
     `:on-action' parameter.

 8.) Configurable notification types
     For example:
     - email
     - notifications-notify
     - emacs-window (like the default in appt.el)
     - custom function

 9.) Configurable notification period
     How often the notification function must be called (once per day,
     once per minute, etc...)

10.) Configurable notification duration
     This applies only for emacs-window and notifications-notify: how
     long must the notification be visible.

11.) Crescendo notifications
     Imagine, deadline is in 10 days. So a silent notification once or
     twice per day, saying it's time to begin to work, could be nice.
     But when time is getting shorter, only one hour left, bells will
     ring and the whole screen will blink red and green...

TIA for any feedback!

-- 
           Peter