Can’t carry anything smaller than a burrito. Can’t eat with a spoon, either. I can make a sort of hook with my hands, which is how I control the joystick on my powerchair. But I can’t tighten my grasp. That’s fairly typical of quads.
That’s why “handsfree” means really handsfree in my particular situation.
If I’m wearing something in a wristband style, I’m going to be wearing it all day. That’s OK, I’m hoping eventually for a smart watch that works for me. But not something I have to slip on and off as needed to trigger a particular device.
Currrently I use very short range proximity sensors on a number of devices in my home, as I mentioned. I expect the technology differs somewhat, these were all storebought devices. A typical range is 2 to 4 inches. It may be that some are motion sensors and some are infrared and some are a trip beam, but they all work well.
The soap dispenser is a cheap one made by Emerson with a red light that’s visible at all times. I suspect it’s a trip beam of some kind.
The trash can is an expensive one made by Simple Human that has a lot of cleverness built in. The initial trigger range is very short, about 3" right over the sensor. But once the lid opens the trigger range extends to about 15" so the lid doesn’t close again while you’re still putting stuff in. No idea what that technology is, but it’s not a trip beam, it requires motion over a horizontal distance.
The Sharp proximity sensor my friend mentioned uses two infrared beams that it triangulates to estimate distance, but it’s set to no more than 5 centimeters, so it’s mostly used to keep things from running into walls and for touchless light switches in hospitals and labs.
Apple iBeacons define the “immediate” range based on signal strength, but it means really really close. Used in stores to allow a shopper to interact with a specific product or for ticket dispensers. Obviously you don’t want your ticket to print while you’re 12 feet away in the queue. Apple has four ranges altogether, I think, and you set different actions for the different ranges.
So two to four inches seems practical to me for a touchless switch.