Android: Not all messages are created equal. Unfortunately, notifications for those messages usually come in a one-vibration-fits-all style. Mumble! allows you to customise notifications based on the content of the messages you receive.
This tool overrides the vibration settings of the SMS app you use normally (though you'll still use that app for sending and receiving messages). Mumble! can make your phone vibrate more for longer messages and less for shorter messages. It can even completely ignore useless brief messages like 'k' or 'lol'.