Honeywell YTH9421C1002 Visionpro IAQ With EIM : Any WIFI Compatible Thermostat ?

I have Honeywell YTH9421C1002 Visionpro IAQ thermostat with EIM. I see only 3 wires coming to the thermostat and being used. The EIM is in the attic. I am interesting in replacing this thermostat with WIFI enabled ones. I don't think I have an option to run extra wires to the thermostat. Can anyone suggest which WIFI thermostat can I replace my existing one with? I am assuming I will have to change EIM unit also? I read all the forums and everyone talks about wiring, I only see 3 wire going to my thermostat. Any suggestions on wifi thermostat that I can use with this EIM or replace will be appreciated Thanks in Advance.