Hi, you could use the AlarmManager. You can set events at a specific time and also if they are repaeting or not. You are free to start an service (for playing sound) or start an activity. Just have a look at Alarmmanager and PendingIntens. Its not that hard.
Yes, if you would like to play a sound the alarmmanager should start an service so that it's not blocking the UI-Thread. Im at work right now, i can give you an example this evening, but google might help you sooner