If you happen to be on a capped data plan, you'll know all about using certain apps sparingly while monitoring roaming settings like a hawk. But while it's seemingly obvious that a YouTube binge is going to quickly use up that precious quota, Apple's iMessage is a comparatively silent culprit. After all, you can send images, videos, audio clips and text with relative ease, and unlike with WhatsApp and others, they're not heavily compressed. If you want to keep abreast of iMessage's data-usage habits, checking the amount of cellular MBs used is possible at stock level, and although the feature is a little obscure, you can easily access it with just a little bit of navigation.