Yep it's ridiculous that they don't at least add the option for a beep etc. every X minutes until you acknowlege a missed call/text. Every cell phone I've had since the 1990's has had that option. I understand it might use more battery, but give people the option. Yes a lot of people find it annoying, but for many business people who are not on the phone 8 hours a day but still need to know when they get important calls it's a great feature. You would think business/professional users would be demanding this feature bigtime, especially with no LED to be a reminder of missed events. Essentially if you don't hear the phone ring, or are around it for 20 minutes after it rings, you are never going to know you missed a call unless you swipe the screen or unlock the phone.
It's like having someone pick up a landline phone every 30 seconds to see if someone is trying to call them.
All apple would have to do is in the "Repeat Alert" screen add an option for "until acknowleged" or "until viewed" etc.
Evidently Apple just can't imagine anyone ever being away from their iphone for more than 20 minutes (the longest time frame you can set it to remind you if you've missed a call, text, email).
Continue to request it as a feature, maybe someday apple will listen.
http://www.apple.com/feedback/iphone.html
And Apple wonders why so many users jailbreak their phones.