Since TreoAlertMgr doesn't seem to work on the T600, I made a workaround for getting persistent alerts when receiving SMS messages. I created a ringtone that has an escalating bell noise that goes off every 5 minutes for 2 hours or until you acknowledge it. It is basically a 2 hour midi song with mostly silence, but the good thing is that it is only a 5k midi file. Also, the sound begins with a few seconds of silence, so if you are holding or watching your phone as you get the sms, you can acknowledge it before the bells start. You can download it at http://www.pursuitwatch.com/alertpersist.mid

Unfortunately, it doesn't work for voicemail alerts because that seems to use a different sound that we can't change.