I don't know if the Airport supports webcams, but it sounds like a Wi-Fi camera would work for you. We own the Linksys WVC54GCA and a couple of Airlink101 Wi-Fi cameras, which all work fine with iCam.
Realize that iCam requires the iCamSource program to be running on your computer, even for IP cameras. This is due to the firewall/NAT piercing techniques used by iCam.