Question about thermostats


I am hooked on this whole automatiom thing.
The next thing I want to do is to add more functionallity to my thermostat. Currently we have not so smart thermostat with limited programming. I does what i want it to do, but i want to make it a bit smarter.

what i want it to do is not to run at specific time, but instead turn on when there is a movement in the house in the morning and shut down when everyone leave the house. We all run out at different times and its waste to make the thermostat to turn off 8:00 am as the family may be long gone by now.

I have traditional 4 wires going from the heater to the thermostat, which i do not want to touch.
I need your advice on which thermostat to get:
- RSC TR16 or TR40
- Aprilaire Model 8870 Thermostat

It seems that both can hook up to Elk.
i purchased the Elk M1 Gold package and i think it came with thermostat interface. I also have network interface attached to elk. Will i have difficulties attaching thermostat interface as both seem to run via serial interface?

I was doing some research online and now not sure if this will work for me
I really like the RC-80B byHAI

the online spec says:
"For use with systems using 24V AC or DC controls (20-30V)"

As far as I know my thermostat has 4 "AA" battries. Not sure if its for backup or the device is powered by these batteries. All I can see is that 4 wires are going from the heater to the thermostat.

Any ieas?
If you are thinking about adding touchscreen software to the setup, I would save money and go with the TR16. The TR40 functionality doesn't get used when tied into a full automation system that takes over.
I think both the Aprilaire and HAI thermostat will need both the original wiring to your furnace and also a serial cable to the thermostat from the elk. The RCS has a box you can mount by the furnace, run the serial and thermostat wire to that and then you can use your original wiring to the RCS "thermostat" from the RCS box by the furnace.

You will also need the ELK Serial M1XSP for any of the 3. Look at the M1XSP installation manual for details, it has explicit wiring diagrams for all 3.
Thanks. but will I also need to drop a 12V /24V to power the thermostat? It looks like HAI requires additional power to operate.
As pointed out above, the 24VAC is already supplied by the existing thermostat wires when using the HAI. In a few instances when the furnace supply is weak, there is a stuttering problem, ie stat turns on the heat, power drops when furnace starts, stat resets, furnace turns off, and repeat... If that happens, HAI sells an isolation transformer to fix the problem. My power is sufficient, so I cannot tell you how the isolation tranformer is wired.