You can certainly use Flash Catalyst to prototype your designs for a tablet or smartphone, but none of the components that Flash Catalyst uses are touch aware. Also Flash Catalyst does not use any of the new mobile portions of the Flex Framework, so none of the advantages that exist in 4.5 for mobile can be accessed.
If you intend to target mobile devices you are either going to have to use Flash Professional or Flash Builder as you development platform.
Hopefully the next version of Catalyst will be more mobile friendly.
I Hope so
Thank you Chris