We want to be able to control our robot with something that is handheld and wireless. Trailing a wire to our robot would make little sense. Having seen how our robot drives in Chapter 7, Drive and Turn - Moving Motors with Python, we will want a control system that affects the wheels in a direct way.
One way to do this would be to use a Bluetooth joypad. There are a large number of these on the market, which may require specialist drivers to read. Bluetooth has a habit of dropping pairings at inopportune times.
However, you already have a handheld device, in your pocket, your phone. It has a touch screen, capable of reading finger movements. With a bit of the right code, you can display the video between controller bars, creating a kind of robotic periscope you can drive around and see (it's quite tricky to drive on camera - harder than overhead)....