Short answer: you can't. The e-ink Kindles do not support status bar modifications.
As for "real apps" - if you're registered with amazon.com, you may be able to download some
active content. If you're registered in an amazon store anywhere else in the world, you're a second-class person and are not allowed to download any active content.
Or, you can head over to the developer's corner sub-forum and see if there's anything there for you. (But no status bar modifications either).