Personally I have only found cables with relatively weak magnetic power. Where does one find these strong ones, in particular for prices like you mention? It doesn't seem to be a well-advertised property, so it's difficult to tell if they are actually strong ot not :/.
The $59 price still includes worldwide shipping.
> That you have to carry such contraption around and find a place to tie it to.
I mean you are already carrying a laptop, and probably a charger with cables, so carrying a magnetic cable doesn't seem a big stretch. You would put it to the same bag with your other laptop-related accesories.
It is also quite popular to wear pants with belt loops, which would seem suitable for tying this one. Granted dresses and skirts have these less commonly; even then perhaps one could use a belt. For sportswear I don't have a good suggestion.
I notice you refer to these "better ways" yet you don't enumerate any. At least I wouldn't consider accelerometer and radio-based solutions proper alternatives to this (unless using proper latency-based distance measurement, I wonder if this truly can be implemented for less than $30). The camera solution I proposed might be realistic one, but it eats battery.
> That you have to carry such contraption around and find a place to tie it to.
If you're the type of person who uses a laptop lock, I could see something like this being a welcome enhancement. But in that case it would be most practical if it were built into the lock itself.
It's the same USB magnetic cable that you can buy in many shops for $2.
> but what is comically impractical about this?
That you have to carry such contraption around and find a place to tie it to.
If you have to spend more than $30 for a custom device you can detect if a laptop is being moved away from a table in many better ways.