I'm developing a todo list application. I'm looking for any way to alert the user when a task becomes due, even if the app is not running. Is there any way to set the program to run at a specified time w/out user interaction? Or a way to bring up an alert anyway?
Edit: How can I add an item to the calendar?
Your best bet right now is allowing users to add reminders to the Calendar - without the push service, there's no notifications without your app running actively.
But even once push is released, that won't enable you to have the application independently alert the user. You would have to run a server that would push notifications to people once a task is approaching due, which means you would have to have everyone's task list synced to your server.
I asked a related question, and the answer provided was very helpful: http://stackoverflow.com/questions/350128/is-the-iphone-cron-able#350136
As has been made very clear by Steve Jobs himself, the iPhone SDK will NOT support background processes. In addition, there is no API to access the calendar on the iPhone.
If these things are important to you, you should file an enhancement request: Apple Bug Reporter