Text Replacement App

I was wondering if anyone has created or know of an app that does text replacement similar to the blackberry text replacement program.

Ie: when your typing a text and you press "u" and then press space, it will replace it with "You".

This would have smartcase enabled, and will allow people to enter in thier own custom words and macros.

goog = google.com
u = you
ur = your
bb = blackberry
droid = motorola droid
fb = facebook
tw = twitter
gc = google chat
*date* = inserts current date
*#* = inserts phone #

The list could keep going on and on.