For example, if I used
Application.getApp().getProperty("foo"); in the onUpdate() function of the watchface view would it have a significant impact on rendering and consequently battery life?
This is the simplest implementation, but if it is going to negatively affect performance then I will use the alternative onSettingsChanged() method instead.
What would probably be useful in the API documentation are metrics for various function calls, since I would guess that some involve simple memory reads, some require communication with hardware and others require reading from persistent storage. This would then help us tune the performance of critical parts of our apps, such as onUpdate(), by minimising the most expensive API calls.
