iSkoot automatically forwards Skype calls from your PC to your phone, including your cell phone.
iSkoot uses an Internet out-going dialing to connect your cell phone with your buddy systems or other Internet phone service. Out-going dialing is the ability for your PC to call a phone number. iSkoot uses your PC as a bridge between two calls to make a local call to your phone, and then connects you to any PC or phone in the world over the Internet. You are charged by your out-going service provider for the local call; the connection to a PC is free, while a connection to a phone will be charged at outgoing rates. iSkoot currently works with SkypeOut.
From what I can gather it's not quite as easy as they make it sound, and it's not free, but it does seems like a good service for Skype users to have, especially for those who need to make lots of expensive international calls.