RemindYou is a native iPhone application published for “jailbroken” phones. To use RemindYou, you must first jailbreak your phone using your method of choice. Once complete, you may install RemindYou using Installer.app or by manual download.
RemindYou updates your iPhone's lock screen every 15 minutes. If you install new wallpaper or enter an appointment directly into iCal, you will need to use the "Apply Changes" button in the RemindYou app to make it appear sooner.
New application comes with a 14 day trial and then costs $19.95 USD.
P.S. By the help of RemindYou you will never miss another meeting, conference call, or soccer game because of a dismissed alarm or information overload.