Voicethread is both a web-based and app based tool. It does require email verification to use your account. Once a student has an account, he or she can respond to your creation with text, writing, voice, or video.
Click here to view my example of a flipped lesson on myON.
Click here to view my example of an entry event for a project.
Ideas:
Load pictures or video of a famous geographical location into voice thread and ask students to respond with facts they know about the location.
Load a video, annotate it using the voice thread pen, and ask students to respond to the video.
Create a flipped lesson using screenshots and ask students to respond with "a question I still have."