A group of researchers in Israel have come up with what they are calling the "sniff controller," an apparatus that looks quite a bit like a hospital's nasally inserted oxygen tubes, but allows for one to control something like a wheelchair with a breath.
The obvious upside is that the sniff controller adds another way on top of mind control and the like to move a wheelchair — which is crucial, considering using one's arms isn't always an option.
The downside? Apparently, the sniff controller isn't as easy as breathing, and can take quite a bit of practice to use. It requires the kind of control over your "soft palate" — the back, roof of your mouth — that a lot of people don't have, but once you get the hang of it, comfortable control comes quick.
The basic functions are easy. Two sniffs out, for instance, would send the wheelchair backwards, while two in would move it forwards. For the people who could wrap their nose around it, they were moving electric wheelchairs around in as little as 15 minutes.