http://www.memoryexpress.com/Product...0%28ME%29.aspx
Wireless G security cam, comes with software.
Otherwise, you'd have to do a search for "Freeware security cam software" and then maybe do a cable run with repeaters to enable a usb camera to be used.
Then there's the setting up of firewalls(only the port accessability) and user accounts to restrict your webcam unless you want it public.
And then there's the bandwidth cost estimation as well, especially considering the soft cap on bandwidth with most of the providers.