I also attached a laptop to a treadmill at home, but the static electricity from the rubber mat kept zapping the laptop.
The best result was a laptop on an exercise bike. But the bike couldn't have a high resistance or I would lose concentration.
Nathan Fielder wears something like this in The Rehearsal. Google tells me it is called Connect-A-Desk.
Honestly, it's never seemed hard to me and I don't remember a time when I was not able to walk while reading without bumping into things. Even as a student when studying for exams, I'd walk around in circle in my room reading my textbooks, for some reason walking helped to better remember...
I can only do this with books. With my phone I am too focused on the phone to work in two visual modes at the same time, which I guess supports the claims.
Still have complete awareness of your surroundings but still be able to read.
I'd argue that's a much more useful "killer app" than recording everyone around you without their consent.
I'm addicted to reading, I take my kindle and phone everywhere, so will grab them when I'm walking, taking a shower, waiting in line, going to the restroom... Between my kindle and my phone, I read a lot more books than I ever did but I don't digest the information as much as I used to. I also don't make as much associations between what I read and things going on in my own life. So, in a way, despite reading a lot more, I don't think I benefit as much from it.
Now, I'm purposefully forcing myself not to reach to my kindle when taking a walk so that my mind can wander as much as I do.