internet access

I have a T-Mobile individual plan and looking to expand into a smart
phone (e-mail and internet) and a data card for the laptop to access
internet (through T-Mobile network). Will T-Mobile Total Internet Add-
on (20$/month) do the work for both? What data cards should I be
looking for for optimum performance? How does it work with roaming
through other carriers like Cingular or Suncomm?
Thanks