...and it seems you can't use this feature with an iPhone (yet?).
From their "web client": Android, BlackBerry, Windows Phone, BlackBerry 10, and Nokia S60.
(In all fairness, my guess is it's pending acceptance of a newer version by the iOS/iTunes review team, but I really hope that's the case.)
EDIT: Scratch that. They're not providing it on iOS because of how convoluted their approach to a web client is. What they have to say: "Unfortunately for now, we will not be able to provide web client to our iOS users due to Apple platform limitations."
From their "web client": Android, BlackBerry, Windows Phone, BlackBerry 10, and Nokia S60.
(In all fairness, my guess is it's pending acceptance of a newer version by the iOS/iTunes review team, but I really hope that's the case.)
EDIT: Scratch that. They're not providing it on iOS because of how convoluted their approach to a web client is. What they have to say: "Unfortunately for now, we will not be able to provide web client to our iOS users due to Apple platform limitations."
http://blog.whatsapp.com/614/WhatsApp-Web
Yeah, right.