From reading a review on the SmartPi, it is designed for the purpose of measuring energy consumption of an electric utility customer like a home or very small office. It is much like the EmonPi.
The only way the SmartPi could be of use in a car would be to measure the unrectified AC coming off the alternator...everything else is DC and the SmartPi sensors are an AC current transformer. As many auto alternators have the rectifier diode built in, access would be a problem. Furthermore, the RPi runs on 5V DC and the 12V DC available at the cigarette lighter would destroy it instantly unless regulated down to 5V...can easily be done but why bother with a SmartPi.
There are lots of things an RPi can do in a car but the entire electrical system runs at 12V DC and the SmartPi's AC current transformers would be of little use in that setting.
Installation of the SmartPi in your home is potentially dangerous and I do hope you will have it done by a competent electrician who can do it without killing himself or you, or setting your home on fire.