Writefull is a light-weight app that provides feedback on your writing by checking your text against databases of correct language.
You can use Writefull in any writing tool - from MS Word to Gmail. Simply select a piece of text, hit the short-key to activate the Writefull popover, and choose one of its five options.
Writefull has been featured in:
Check how often your selected text is found in the language database.
Enter two chunks and compare how often they are found in the database.
Check out examples of your selected text in the Wikipedia database or on the Web.