I Spy certainly looks like one of the oldest car games around. It is one of the simplest mental-visual games around. Games, as in all things, are most fun when they are simple. It certainly fits the bill as one of the better ones in indoor kids games.
The game also has so many variations not just as a car game but both as indoor and outdoor games. The object is changed to people and they are usually played in classrooms (when the teacher has not arrived yet, etc.), cafeterias, or school grounds where there are people.
The game of looking
These car games had a long history themselves. Maybe, they were developed as soon as the first cars rolled down the streets. Whatever the story is, it is better than the current electronic gadgets that grab the entire childs attention and only to himself.
This old game (and other games like it) has given the chance to have the parents interact with the kids and with themselves. Moreover, this is one game where the kids can use their imagination and creativity.
At this point in todays technology, kids are being bombarded with all sorts of electronic stimuli. Some of them are portable (game boxes, phones with games, etc.) that they can bring out of the house.
Sadly, all of them had taken out the childs chances to think. Most of them are all about finger and arm dexterity and reflexes.
The game
In playing with little children, it would be good if you can help build your childrens understanding of, say, color. You could say, I spy with my little eye, something moving with the color of.and mention the specific color.
If it gives them some problems, you can then go with explanations like a cross between and give out familiar colors. After some time, without their even knowing it, you had given them some lessons on colors (identifying it) and alert meticulousness (looking for it).
Playing with more than one child is even easier. One person goes first and the first person to guess the object or person will get to spy the next object. When the child guesses the object, then it is that childs turn to spy something.
You can keep it going and forth with them. If your turn comes up, you can then put it the little color and alertness lessons in your spying declarations.
Older children
If the child is a little bit older, you can use letters. I spy with my little eye, something starting with the letter B. If the child knows some basic reading skills, you can easily play this game with him or her.
If one of you never guesses the object and gives up, the person who did the spying gets to take another turn. Or you can get to be specific: I spy with my little eye, something that begins in letter a, so red and so delicious etc.
Other car games
There are many other car games as there as children who can think of games like it. Which make indoor kids games more colorful, interesting, fun, funny, and never boring.