From GameBrew - a wiki dedicated to Video Game Homebrew.
DS Sleep (Frenxh) is an application that act as a sleep function for the NDS, originally created for those who listen to music while going to sleep.
Enter the time (in seconds) and it would turn off the console when the time is up.
Up - Pause
Down - Resume
Left - Reduce 3600 seconds (1 hour)
Select - Display info