You can do this using Applescript, so you can do this in bash using the osascript command:
osascript -e 'tell application "Quicksilver" to show large type "Hello, world."'
I think the βBig Typeβ was previously available in the services menu, but I do not see it in Snow Leopard. Maybe I'm wrong. A similar function is found in the address book - right-click on the phone number.
source share