VoIP is a wonderful thing, allowing you to make worldwide calls over the internet for free. But that means you need access to the net, and if your smartphone doesn't have WiFi built-in (as is usually the case), then you're out of luck.

But that might not be the case for long. Currently, a beta is on-going for a new mobile service called iSkoot. The service will allow you to call your Skype contacts from your mobile phone.

The service isn't in full swing yet. You can download a free trial version, and it seems that iSkoot subscribers will pay a flat monthly fee once the service becomes active. Many popular phones like the RAZR V3, Treo 700p, and w600i can run the software, but the list of supported handsets is still limited.

What if Someone Wants to Call Me? Skype users will also be able to call your phone, but they'll have to pay to do so (through SkypeOut).

Extra Costs: You'll also need a data plan to get the iSkootMobile software working. See the program's requirements for more info.