These toy cars are modified for sip-and-puff controls, where one lightly sucks or blows air as an interface.
If you have certain disabilities, use of your hands can be difficult if not impossible. An alternative is an interface known as sip-and-puff, which allows for control of electronics by producing a small air flow with your breath. In the build shown in the videos below, Bob Paradiso integrated this type of command into two types of RC vehicles.
To operate the first vehicle, one simply uses puffs to go forward, while sips make the car go backwards. The second is much more advanced, with a double-puff making the car go forward, a double-sip for backwards, and single puffs and sips to turn left or right.
There are many sip-and-puff controls on the market for various things, but they can be expensive or difficult to customize. What I’m showing here is an extremely affordable, simple to build, and fully customizable sip-and-puff setup used to control two different remote control toys that have very different controls.
You can see Paradiso’s writeup here and check out the code on the project’s GitHub page.