Write an intro to the section here, but it'll be the intro before the chapter eventually.

Paste in a very summary version of the radio appendix from 1st Ed. Wrap up in some of the slide language about ubiquity of featurephones, sensors, etc.

Make sections (with charts) on speed vs. latency and discuss that in the constraint/capability thing. Mobiles are plenty fast, but have intrinsically high latency so you have to not test on wifi or desktop...