I’m not sure how I missed this one, but I just noticed that in iOS 6, I can change alert vibration patterns, and even create my own patterns. Very cool.
Go to Settings > Sounds, then select one of the alerts to customize. Text Tone, for example. Scroll all the way to the top of the page, and tap “Vibration”. From there, select a pre-defined vibration pattern, or scroll down to “Create New Vibration”.
To create a new vibration, just tap on the screen. Hit “Stop” when you’re done. Name it, and you’re ready to use it as an alert vibration.