The home screen already has some dynamically updating information. The calendar changes with the day. And badges appear as push notifications are received. Having the weather app icon change once or twice an hour shouldn't have a noticeable impact on battery life or performance.
Performance is one thing, but I'd say distraction and icon recognition are far bigger issues. The calendar icon changes
once per day. The icon looks largely the same, just with a different number. The weather icon would drastically change depending on the weather, from yellow on blue on a sunny day to grey on black for a cloudy night. Personally, I think it would be better to scrap the app altogether and make tapping on the weather widget display an inline 5 day forecast in Notification Center. The app feels like a widget anyway, and this would solve the icon problem.
moving clock hands on the Clock app
Ignoring the fact that the clock app isn't actually designed to be an app that tells you a singular time and is instead a world clock, alarm, timer and stopwatch,
and that the current time in your locale is
everywhere in iOS,
and that nobody would ever even consider looking at the Clock.app icon to find the time: can you imagine how distracting it would be to have the second hand ticking away all the time? The movement would continually draw your eye to it. Ugh.
You can't possibly argue that it's worth the development time, battery drain, and user distraction just to have an icon of a clock that needlessly tells the time. Can you?
