EXIF Viewer is beautiful App along with Photos Extension, Recent Photo's EXIF Widget and iMessage App. It is well crafted app for professional photographers who are serious about their work. It's an universal app, buy once, use on all your iOS devices (iPhone, iPad, iPod Touch).
Update: Sketch Tree expired
Sketch Tree is a mobile drawing application created specifically for creative professionals. Its painting and drawing function is very groundbreaking, with realistic brushes and breakthrough watercolors. The canvas can be enlarged 64 times with a high-precision grid display, and the artwork is accurate to the pixel level. Full-featured painting tools, with over 80 exquisite brushes, erasers, smearing tools, ruler, cutter, filling and roller auxiliary tools, color picker, and an advanced layers system that can import background images and sketching, black ink, color painting, color separation, sharpen layer processings. Adjustment for brush size and transparency, unlimited undo and redo, continuous automatic saving, simple and easy to use interface, even beginners can quickly get started. GPU hardware acceleration, you can create beautiful sketches, fascinating pictures and wonderful illustrations anywhere and anytime. And you can share your works on social networks.