Apple added support for third-party apps right in iMessage as part of the iOS 10 release, and thus far the obvious use for this feature has been stickers. Everyone loves slapping stickers in their messaging apps. But, lest we forget, iMessage is primarily an app for communicating with words. And it's entirely possible that some of your friends don't use there words well. If that's the case, consider the Grammar Snob sticker pack: it's a bunch of red-pen corrections for common mistakes that you can slap on you're friends' errant chat bubbles.
— John Haney (@johnhaney) September 15, 2016
Besides the obvious one (to / too / two, your / you're, we're / were and so on), the pack also offers some corrections for commonly misspelled words like espresso, figuratively and more. There are also a bunch of generic cross-out and insertion stickers, so you can really fix the horrible messages your friends send you. The app will set you back a buck on the iTunes Store, and it's probably the smartest use of stickers we've seen thus far.
Of course, just be aware that being a grammar snob is often the quickest way to make your friends ignore you completely. Still might be worth it, though.