All iPhone vibrations are not created equal. At least, not if you have upgraded your iPhone to iOS 6, the most up-to-date version of Apple's mobile operating system. It didn't make the keynote address about the new iPhone, and it's way deep in the settings. But if you're always checking your phone because a Facebook message vibrates just like an important SMS from the boss, you'll never go back to the default.
Open your iPhone's Settings (this won't work for iPads). Head to the "Sounds" area. Look for "Sounds and Vibration Patterns." You'll see a long list of all the things your phone might notify you about: phone call ringtones. Choose an alert incidence, then scroll to the top, above the ringtone choices, to choose a vibration type for when your phone is clicked into silent mode. Settings > Sounds > Sounds and Vibration Patterns.
Under each alert type (Ringtone, Text Tone) at the top, there is Vibration. Select the vibration type there. "Heartbeat," "S.O.S." (you know: dit-dit-dit-daaa-daaa-daaa-dit-dit-dit), and others. But even more interesting is the custom option, down below the standard choices. You get a screen on which to press and hold in intervals, or tap out a rhythm that will be significant for the type of alert you're customizing. Each vibration pattern you set up is saved, with a name you choose.
This custom vibration mode isn't just available for the settings you can see in Settings. You can head to your contact list, click a name, and create yet another vibration pattern for that person. And here's a really distinctive setting: you can set up distinct vibration patterns for each mail account you've set up.
Custom vibrations aren't something everybody needs, which is why they're easy to overlook in the iPhone's Settings. But for those who want some distinction, and a chance to ignore the stuff that doesn't matter, they sure are nice.