Aethers

It's a small transparent pixel loaded from a website (assuming the email client loads HTML). I'd make a unique image called mywebsite.com/jaclaz_read.png and when that image was loaded I'd know you read my email.

> But cars aren’t going away anytime soon, certainly not in the suburbs or in cities like Los Angeles, and we can’t just wish away lots in which to park them.

When we have self-driving cars, nearby parking lots won't be as much a necessity since the car can drop you off at the door, then drive itself to a parking space much further away (or to another customer, in the case that it's a self-driving taxi).