I've looked up the IP/Ethernet thermostats available from four different vendors, and their products don't seem to allow for direct web-based access to the thermostats by the end-user. The way they do it is that the thermostat communicates directly with a server operated by the manufacturer, and the end user accesses their own thermostat via web interface hosted by the manufacturer.
Does any thermostat manufacturer offer an IP-thermostat that contains it's own web-server that's directly accessible by the end user to program the unit and allow for direct monitoring, view temperature and performance logs, allow for e-mail alerts, etc? These are all trivial functions that you'll find on any $100 IP-based webcam.