Its a very cool video, BUT, something is eluding me...
From what I read i the github you shared, the mesh connects in adhoc mode, meaning that there is no Master/Slave relation, however, to the best of my knowledge, adhoc is only possible between no more than 2 devices (?)... (after googling, I see I am wrong.. need to look deeper into this)
Plus, the addition of a webapp, in my way of viewing things, makes the smartphone a Master device, which controls any other "smart block" that get's added to the network... the fact that the "smart blocks" react to another block being added or removed may be explained by the webapp behaviour too...
I will first gather a few ideas and notions, and figure out what would be the better approach to a similar behavior, but without the webapp...
What I can see as a "real world" use, is a esp based "smart display" (like the nextion) which will react to other "nodes"(sensors) being added to the mesh and show their info... I have 2 ESP to try out, plus a few smartphones that can simulate other nodes.. will see how that Goes, maybe i'll get a few more ESPs