Yes ivtec3......ECO is the system in which engine stops at break and restarts on accelerator.
I have been going through market. Vitz 06 unregistered (ECO or without ECO) will be easily available around 10. (do let me know if any registered is available obviously it will be of less price)
Some showroom boy told me that in ECO cars 2nd battery which is underneath the front passenger seat does not need maintenance. It is life long. Just protect it from water. This need to be clear here. One more thing if this system gets out of order then what, is there any button or way to bypass this system.
I also noticed that showroom owners / workers have not much knowledge about specs of these vitz.