Use Remind to communicate with your students. You can use the website for easy set up, then use the app so messages automatically are sent to your phone like text messages. You can mass text your students or text them individually.
Send students on a virtual scavenger hunt with this app. For the free version, there can be no more than five teams. The questions can have text, picture, video or even gps responses. You have to make the game on a browser, but students use the app to play.
Use your phone as a pdf scanner! Use this app (or there are others) to take a picture of a document and save it as a pdf. This way you never have to worry about finding a scanner again.