The Nest wi-fi thermostat is created by Tony Fadell, who worked at Apple on the first 18 generations of the iPod and the first three of the iPhone, and the not surprisingly the design of the thermostat is one of the most striking features. The Nest functions very similarly to the Ecobee wi-fi thermostats, but has some features not seen on Ecobee. The one that stands out the most (may not always be practical) is the activity sensor that works with the Auto-away feature.
From the Honeywell Prestige 2.0 website:
"Connects to the Internet - Monitor and control your HVAC system over the Internet from a PC, smart phone or tablet (with Total Connect Comfort Services)".
The Filtrete 3M Radio Thermostat is one of the lowest cost wi-fi thermostats with mass market appeal selling at under $100. There is an iPhone and a Droid app for this thermostat. Like the Ecobee thermostats, a common wire ("C") wire will be needed to supply power. Also like the Ecobee thermostat, the Filtrete 3M Radio Thermostat can be programmed for vacation and holiday schedules. Radio Thermostat sells other thermostats as well, but the 3M partnership will allow many homeowners to get a wifi thermostat.
The Ecobee Smart SI thermostat is the lower cost version of the Ecobee Smart Thermostat. Like the Smart version, it has wi-fi and can be programmed over the internet and through the smart phone app. The biggest feature the SI lacks compared to its bigger brother is the ability to connect with Ecobee Smart Plugs through the add-on remote sensor module.
The Ecobee Smart Thermostat is the company's first product for the home energy market. The web enabled wi-fi thermostat enables users to access their thermostat from any computer connected to the internet through the Ecobee web portal. Users with an Apple or Android device can access the thermostat from the Ecobee App. The web portal allows users to update their thermostat settings, set vacation schedules, view reports on their system's performance, and set alerts and reminders.