The BlackBerry allows to include automatic signatures on every email that is sent from your mobile device. This is convenient so people know that you are writing your email from a mobile device. Unfortunately there is no built-in functionality to do this also with SMS text messages but this workaround can help you.
Using AutoText for signatures
The BlackBerry has the built in functionality of auto text which is used to correct common spelling mistakes but which can also be used to replace certain text when you enter certain text. The idea is to setup autotext for a special phrase which will then be replaced with your signature.