I'm afraid not. Not sure why Apple missed out on this. This should have been given as an option for the users as I consider this as a basic functionality of a hand phone.
I feel that the bundled tones that comes are just too soft and short. I missed many messages since I started using the iphone especially at night when I'm deep asleep and urgent matters need to be looked into. If only the tones could be repeated twice or trice per SMS. That would be great.
Let's hope the 2.1 FW would have some good news for us.
I agree, I had a app on my treo, that would bug me every 5 minutes with a loud tone if I missed a text, phone call, voicemail, etc. It would be nice to have something like that implemented.
I'm glad to be able to get louder phone ringtones, the stock ones were pretty quiet also.