There are far more interesting apps out there, but sometimes a brother's just gotta print something. Printer (and sewing machine!) company Brother now has an iPhone/iPad app, which prints wirelessly but can also scan to the devices, too.
iPrint&Scan is a free app, as you'd expect when you've already paid a few hundred for one of their printers. Printing can be done directly from the iPhone or iPad's Photo Album, or even from the iPhone's camera, but to scan a document or photo you'll obviously need to place said document in the printer to scan it to your iDevice. Sadly the app is not advanced enough to guess which document you wish to scan in.