Home Thermostat that keeps logs of activity -- does this exist?

I have used an HAI RC-80 thermostat for about eight years. It has an RS-232 serial port and a command protocol to access all the settings and status.

There are only three wires to connect for the serial port (TxD, RxD and ground) and I wrote a perl script to interface with the thermostat.

The script is available here:

I use RRD to graph the data points (once per minute) and use different colors depending on the heating mode (heat/fan/off). Examples of the graphs are at the above web page.

TekMar thermostats have monitoring functions that record all usage totals but not TOU.

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We're trying to get our energy usage under control and thanks to a smart meter we can how see our household energy usage at 15 minute increments. What I'd like to do is find a home thermostat that'll keep logs of when the HVAC system comes on and goes off plus possibly a log of the temp and humidity. Our current thermostat has all this info on screen but there's no log per say that saves it.

Does something like this exist? I can't help but think someone has created one with a Wifi connection or possibly USB port to save the logs to since this would be invaluable information for any home wanting to cut costs.

Thanks --