WeatherKitten (WeatherCat iOS client) V1.0.0 B97 is now available in beta! See https://athena.trixology.com/index.php?topic=3714.0 for more details.
WRT the update rate, it is dynamic based on the type of the data being displayed (a gauge displaying wind direction will set a much higher update rate than a gauge displaying temperature for example), the OS you are running on and the hardware - we found in development it was very easy to end up with cooling fans getting very loud, so what we have now takes the above into account to keep the load down.