OIST stands for Oldsap’s Individual SMS Tones and allows you to set an individual ringtone for each contact.

Changes:

– alarm scheduler: Play sound(wav or mp3), and show a message box
– no more tray icon on today screen
– Remote Control Feature: retrieve unread sms
known bug:
– sometimes the incoming sms tone plays twice
– vibrate option for alarm scheduler not yet working

http://forum.xda-developers.com/showthread.php?t=407933