This little app Hey Tell allows you to use your phone like a walkie-talkie and leave small voice notes for your friends and family.   Sure helps when you are walking and want to send someone a text, just push to talk.  And it is FREE!  You can, of course, add on a little bit and get the ability to “push your voice” out to multiple people.  Could be handy for sending out reminders to a list of say, students.  Just saying.