How to use a(n Android, for instance) tablet as secondary monitor for your computer (running xorg, and presumably Linux)?

This solution is in principle very nice: no restart needed, easy to automatize. On my system, with both the screen and the tablet being 1280×800, it's as simple as

1. xrandr --fb 2560x800

2. x11vnc -clip 1280x1024+1281+0

3. starting bVNC on the tablet.

There are two problems, still unsolved:

1. This bug causes the pointer to be constrained to the phisical screen. The patch provided seems to work, I still didn't try it.
2. the maximum size for the server may be smaller than what you need, so in fact you won't be able to bring windows outside of some invisible boundaries. This is probably easy to solve, but I still didn't find a way.