iPhone - is it possible to "awaken" an app after a certain time?

I was wondering if it was possible to have an "alarm" style app that would run at a certain time? Would the application have to be run and then left open?

I know with multi-tasking on the iPhone 4 a user could open the app and run it in the background. If my original question isn't possible, is it possible to bring an app running in the background back into the foreground after a 开发者_Go百科certain time?

Thank you very much for your help.

Have a look at the new 4.0 feature called Local Notifications. Local and Push Notification Programming Guide

You can use EventKit to put certain alarms. It is however not possible to schedule to launch of your app. You can not bring your app forward like you suggest. You could however send a push notification. The link suggested by Jessedc gives a lot of in-depth information about the use of this.