A macOS app for quick access to WCAG color contrast ratios → https://itunes.apple.com/de/app/contrast-color-accessibility/id1254981365?l=en&mt=12

… wireframing, mockups and prototyping for websites and applications

Wireframes on the fly … an online tool that makes it easy for you to create, link together, preview, and share mockups of your website or application.