If you're even going to have your cell phone with you, you're going to want to read this
Cruisemates Blog Cellular @ Sea Can Be A Rip Off @ Sea – Kuki
As for the Ipad, using it would be the same cost as using the computers in the Internet Cafe onboard, or your own laptop. The cruise line does sell a variety of Internet time packages. Costs can vary from 45 cents to 75 cents per minute of usage depending on the package your choose.