ip phone

Skype is a proprietary protocol, only Skype software can talk the Skype HQ to handle your calls. There's a few companies who have made "Skype" phones that really are just basic phones that talk back to your PC over normal channels and some software that controls the Skype client based on what you press on their phone.

The 7905 is a H.323 only phone, which probably is really only useful in a Cisco CallManager setup. You probably won't be able to use it in any fashion if you don't already have a CallManager setup.