I just checked out SmartSig and I have to say it is very cool. One of my long running gripes with BIS email signatures is that they show up at the very bottom of an email, after all the text in the email - even reply or quoted text. With SmartSig you can change that and have your signatures show up right where they belong. The app lets you choose custom signatures for email and SMS, and you can create and edit them right on your device. You'll need to delete your BIS signature for SmartSig to work properly, but from there you're all set. SmartSig runs on all devices with OS 4.3 and higher and is available for $1.50 in the CrackBerry App Store.