Simplehomenet has the documentation listed for an Insteon communicating thermostat on their website. No product yet. There's an interesting IP thermostat from Proliphix that can be managed from a webbrowser anywhere. Kinda pricey at smarthome:
but maybe an option. Burying 100 feet of cable (having done it a few times) is no fun and has a low WAF if you have to route it through favorite parts of the garden.