I have found what must be the best toy of 2014. Seriously! Magic!
It is called the Anki Drive $149 for the base set with two cars, chargers, and a track. Additional cars are $49, and extra tracks are about $70.
This is "slotless" slot cars for the next generation! Roll out the 3.5' x 8.5' mat, charge up the cars in their futuristic USB garages (in about 10 minutes) and, while you wait, download the free app. Each driver needs an iOS or Android compatible device (and at this time you can either run ALL Android or ALL iOS devices, not a mix).
Now comes the Houdini part! After a brief recharge and program setup, the game launches the coolest tutorial I've ever seen. Put the cars on the track and they start racing (while changing lanes!) autonomously and fast! You'll be given brief driving lessons. At first you only control the speed of the car, then it teaches you how to change lanes. Amazingly, you don't have to worry about steering the tight curves of the track. Like Google-Autobots, these cars know the road. Your job is to strategically work within the track zig-zaging the course while trying to get the best of your opponent.
Like the classic video game Spy Hunter, this game isn't just about driving. Each car has a virtual weapon and force field. So as you drive, you also can disable or slow down your opponent's vehicle. The cars weapons and armor upgrade, just as if you were in a video game. The more/better you play the more/better your car becomes.
The cars charge in about ten minutes and work for about 20. You can play solo or each person can control their own. Up to four cars can be on the track at once. We found the AI opponent to be tough to beat, a real challenge.
You can find more at https://anki.com/en/anki-drive/starter-kit.