Fair enough. Maybe for me the bigger issue is no post-event notification at all if you're out of the room when a call or voicemail happens....I realize that its purpose and your desires for a notification light are not the same, but you made it sound like it didn't work at all.
You can tell the iPhone to alert you repeatedly for a missed text. I don't know why Apple doesn't offer that same option for missed calls/voicemails. I'd settle for a vibrate or reminder tone every 10 min. Hell, even my old flip phone would do that.