I believe RCS has a solution that might be good for you especially if you have a multizone system

They provide a thermostat and a control box and a hub.

Each thermostat replaces the existing wall thermostat. Using the existing wiring you place the control box at the HVAC unit, connect the thermostat to the control box and then the control box the the HVAC system. The control box has a RS485 output (think RS232 for hundreds of feet with no issues) The hub handles multiple control boxes and ends up with a single RS232 port, or if you only have one Zone, then a simple RS485 to RS232 adapter from Black Box will do the job.

the advantage of this approach is

1) uses existing wires, nice looking theromostats
2) opertes by itself, i.e. the thermostats work as before but no auto setbacks
3) The pronto can control and interrogate the system and issue a setback command.