iPhone: If you have one person you tend to message with a lot, Other is a very simple little app that makes sending a canned message to them easier.
Other is kind of like a launcher for messaging a single person. You can set it up with predefined messages, so it's easy to instantly send a message through the normal Messages app to them. If you have a iPhone 6s, you can even send those messages from a 3D Touch shortcut on the home screen.
There's also a share extension so you can easily send something like a URL in Safari to that person with just a couple taps. If you tend to send the same type of message to one person a lot, like that you're on your way home, stuck in traffic, or whatever else, Other makes it just a little bit easier.