Grapholite Diagrams Pro
Let's acknowledge the elephant in the room: $27 is an awful lot to spend on a mobile app. But if you need to create any sort of diagram for your business—from flowcharts to technical drawings and wireframes—then Grapholite Diagrams Pro has you covered. The interface rocks with touchscreen hardware, and the app's superb charm integration makes sharing, printing, and exporting files to various formats a breeze.
Given the (relatively) high entry cost, I'd recommend using the trial version before investing in the full-fledged app, but there's a great chance you'll be hooked once you take Grapholite Diagrams Pro for a spin.