Just a random thought.
You could do a modern take on the old Logo turtle-robot, but with a remote-control car whose movement you could program, wirelessly, via a smart-phone or tablet.
If you're not familiar with Logo, the "turtle" was a simple robot on wheels with a pen attached to it. You sat it down on a big piece of paper and as it moved along the pen traced out its path on the paper. Logo was the simple programming language used to tell the turtle what to do (e.g. 'move forwards 10 units', 'turn 45 degrees right', 'move forwards 5 units', etc). You'd write the program then send it to the turtle which would slowly move around according to the commands in your program, and if you programmed it right it could draw out all sorts of shapes and patterns. The system was for teaching kids the basic concepts behind programming.
But what if instead of the turtle you had a remote-controlled car? Instead of directly controlling its behaviour with a normal RC controller, you'd control it like the turtle, by writing a program that sets out the movements it should perform. Specifying this with a smart-phone or tablet would make sense - the instructions could be sent wirelessly to the car.
Compared to the traditional turtle an RC car would be faster, have acceleration and braking, and could travel over rough and varied surfaces.
Instead of being about drawing patterns on paper, it could be about getting the car to successfully navigate the physical environment. It might be in your backyard, and avoiding trees, going down slopes, traversing small mounds, etc. Where there's obstacles, the possibility for jumps, and so forth. Where obstacles could form signposts for a track.
I suspect that, rather than programming it by telling it to move by a certain distance or to turn by a certain number of degrees, you'd want commands like 'move at 75% throttle for 5 seconds' and '50% right turn for 1 second' (where '100% right turn' would mean turn as sharply right as possible, so 50% means turn half as sharply).
The hope would be that kids would find this kind of thing fun. Rather than having a more abstract goal of drawing certain shapes, they'd have more tangible goals like navigating around the physical space, getting it to do a jump over a curb, etc. That a remote control car can go pretty fast would hopefully make it more exciting, too.
I would imagine that if a bunch of kids got together and they had several of these cars, they could try and race them or set up some other kind of competition (e.g. trying to get the cars to ram each other, maybe to knock one over).
Electronics are so much cheaper these days, so I imagine that cost or getting the necessary parts to do something like wouldn't be too much of a barrier. (And if you are wondering whether I have any thoughts about trying it out, I don't. It'd be nice to try but I'm working on other things at the moment. Just thought I'd get the idea out there).
Of course, there'd be a lot more to think about to think this through properly. E.g. Logo has the equivalent of procedures, which can be useful for drawing shapes and patterns, and these are a form of abstraction you want to teach. Would there be some motivation for utilising procedures if the focus wasn't on drawing patterns?