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.