Anything that’s capable of detecting drones would get hella false positives from birds/bikes/cars/people. There’s a reason radar usually ignores movement under a certain altitude.

You could detect via radio signals, but fly-by-wire drones are already a thing, perfect for short distances, like what you’d need to move a package over a wall.

They’re expensive but not really overpriced. Boox tablets are essentially Android tablets with highly specialized screens.

Eink screens (particularly high refresh rate screens, like what you’re looking for) are still a relatively new tech and don’t have the cost benefits of more matured technology like LED/LCD. The cheap eink screens you see have very slow refresh rates and don’t offer the same pixel density, with harsher gradients.

I’d reccomend getting one used, or waiting for a seasonal sale. I’ve had one for a while and I love it.