My heating system is a boiler with 4 zone valves (Taco). Each zone valve connects via a 2-wire cable to its own thermostat. There are no spare wires nor easy ways to run more cable to the thermostats. I'd like to upgrade each of these thermostats to a Wi-Fi thermostat (preferably one that integrates with Wink home automation). I assume that I can use a Sensi thermostat that uses a battery for power. However, I'd like to avoid changing batteries. Any recommendations beyond a Sensi? Is there a system where the wires are used to get 24 volts from the transformer to the thermostats, and then all signalling is done via radio frequency?