RC toys could be a great addition to your arsenal of gadgets for downtime fun (and to antagonize your spouse/pets)...
AR Drone Thanks to its on-board Wi-Fi system, you can control the Parrot AR.Drone using an iPhone, iPod Touch, or an iPad. It was initially designed for the Apple platform and will be also available for Android smartphones pretty soon. You can also control the Parrot AR.Drone from a Linux PC and a joystick with the navigation software supplied. It's easy to fly and thanks to servos and gyroscopes, it auto stabilize so it won't crash if you haven't master the landing technique.
Orbotix Sphero With 74mm in diameter, and featuring inductive charging, this cool robot is controlled via bluetooth with your smartphone. Think of Sphero as an entirely new game platform – one that moves. The ball in you living room now becomes the object in the game on your iOS or Android device. The company is still working hard to fully develop the platform hoping it inspires developers to make tons of games. You can solve a maze rolling Sphero around on the floor, challenge a friend to a head-to-head sumo match or control a device in your friend’s apartment, from your apartment.
AppToyz Mini Heli This is a micro helicopter that you can control with your iPhone. You just need to use the supplied adaptor to bridge the gap between the heli and your iPhone. The funny part, is that you use the headphone connector (!) instead of the 30 pin at the bottom. Control is easy via the user interface and even that the heli looks small, it has quite a bit of get-up-and-go.
Then, for the DIY'ers out there, if you have the "know how to", you can easily make this one. Control an inexpensive RC Car, with an iPhone. With the NerdKit serving as the bridge between the computer and the R/C Car, it is as an example of how useful microcontrollers can be when they fill the gap that makes complex systems work together, and with an understanding of how the system works, a neat project like this one is achievable as a Do-It-Yourself weekend task.