From the Ars Technica coverage…

From the Ars Technica coverage ( here’s a good user comment the expands on this idea:

“Passive wifi for notifications and downloading stuff like email in the background. If the user starts using the phone, though, fire up normal wifi to get everything faster.”

Originally shared by Henk Poley

Passive WiFi uses reflection of an always on WiFi signal to transmit at 802.11b speeds, but using 10000x less power.