Well I don't have android to test but here is what happens on the iPhone - I'm assuming they use the same RPC methods:
1. Imsanity enabled - does nothing regardless of the image size uploaded (ie the user can upload images larger than the imsanity limit size) I configured Imsanity with a really small size to make sure it would "catch" all images.
2. Whether Imsanity is enabled or not - when I try to upload "original" size image I get an error with no details. The small, medium, large images (which are resized on the phone) will always upload with no problems, but not the original size (even though it is not much bigger than the large size)
So in summary, basically what I see on the iPhone is that a) Imsanity simply isn't doing anything at all and b) uploading the original size image will fail regardless of whether Imsanity is enabled or not.
At the moment I'm pretty much out of ideas because it looks like the plugin isn't even activated via RPC so I don't know why android is getting an error & I don't have an android to test.