Love that book, it also reminded me of his book/short story Fast Times at Fairmont High where they use small devices like this as breadcrumbs to keep them connected to the grid (a mesh network).
Ahh, my bad, he did have a short story called Fast Times at Fairmont High that was related to/in the same universe as Rainbows End. I've read both. Great author.
From Wikipedia [0]:
> Vinge's 2006 novel, Rainbows End, set in a similar universe to Fast Times at Fairmont High, won the 2007 Hugo Award for Best Novel.