Quip gained some buzz when it first launched because it was created by Bret Taylor, the former CTO at Facebook and an engineer who helped build Google Maps. The company's goal is to build the service to write, edit, and collaborate on the go, but right now it faces competition from Evernote, Google Drive, Microsoft Office, and Apple iWork.
Quip's word processor does many of the same things Google Docs does, but with a simpler interface and greater emphasis on collaboration. You can create a new document, add images and checklists, and then share it with friends, family, or coworkers. Others can add text, edit, and comment on the document, and any changes they make are recorded in a simple log. In the mobile app, you get notifications when someone contributes.