This really is (IMHO) a much needed feature.

I'm thinking - SMS notifications via SMS gateway etc...

Linked (related to):
CHD-846 and CHD-1123 , the two "reminder" systems.

Yes Please. Send emails when a task is overdue.

I really love this feature at highrise

I linked this in seb's other forum thread:

http://www.cerb4.com/forums/showpost.php?p=13972&postcount=7

I'll see if I can squeeze this into the 5.2 release as well. The only trick here is sending a notification when the task first becomes overdue, without constantly sending notifications when it remains overdue. However, it may be useful to receive a daily notification when things are overdue (we just don't want it on the cron.heartbeat every 5 minutes).

Implemented in 5.5-dev using Virtual Attendants:

* [Virtual Attendants/Scheduled Behavior] [CHD-846] [CHD-1123] Virtual Attendants can now schedule behavior to happen at a future date. This provides an incredibly flexible way to build reminders and automated followups. For example, if an incoming message is from an organization with a service level agreement (SLA), your Virtual Attendant could schedule behavior in 2 hours to check the status of the ticket and react appropriately (e.g. escalate). Scheduled behavior can also reschedule itself, providing the ability to create loops of behavior that repeat until certain conditions are met. For example, if the duration since the last worker reply is too long according to the SLA, a reminder could be sent to the record's watchers every hour until rectified. Each new reply from a customer could initiate the behavior loop over again. Scheduled behavior is managed by a queue that runs as part of a scheduled job from /cron, which is more efficient than holding up the email parser or worker UI during long-running tasks.