My understanding of it is that they're working within the constraints of WebKit in iOS. Developers aren't able to update the icon in realtime, but if you have a

My understanding of it is that they're working within the constraints of WebKit in iOS. Developers aren't able to update the icon in realtime, but if you have a homescreen webapp it can update the icon each time you launch it. This is a nice workaround, since I used to launch my homescreen weather app every ten minutes, and chances are the temperature hasn't changed much since the last time I checked. I say "used to" because I use the Weather widget in Notification Center.