Burn Note it would be true. Burn Note is a free service for sending messages that self-destruct after they are read by their recipients. To use Burn Note just visit their homepage and start typing your note. When your note is complete a unique URL is generated for you to share. Once that URL has been used by someone else, it no longer works.
Applications for Education
If you have to recover passwords and send them to students or faculty, using Burn Note ensures that they won't accidentally forward that password or otherwise share it with people that shouldn't see it.