I cannot ask the box programmatically how much memory the box is using right now.
But, and this demonstrates some of the confusion that can occur, your question has nothing to do with the topic of this thread. R2D2 uses RAM. The SD card dialog appears when the system is low on NVRAM, a completely different kind of memory.
EnTerr, how would your proposed "size" display work if the app is not loaded? There are two possibilities, but I see issues with both.
1. Display the actual amount of space that the app is currently using on the box. But then GiantMegaGame would appear to use only 4K one day and 20 MB the next day.
2. Display the amount of space the app would use when it is downloaded. I'm not sure we actually have that information, but assuming we do, the number would be fairly meaningless as far as helping the user understand his space usage.
Perhaps what you really want is the amount of space that can't be ejected when the app is unloaded? This would be somewhat more useful, but harder for the average user to understand.
Tangrams 1.1.0 (#59088, 0.0+1.8MB)In this example, neither app has >0.05MB (the round-off) resident - and the bundles are 1.8 and 2.0MB each. I cannot think of a simpler way to represent the situation (the numbers' meaning can be further explained to those who want to know in the forum/blogs; after all this is Konami Komando screen) - but it's akin to locked/wired memory + swappable process memory in the RAM case.
Agario 1.2.0 (#75560, 0.0+2.0MB)