Video message to the beat with Samba!!!
In other words, users simply record a video message and flick to send. As the friend views the message, his or her reaction is recorded and automatically sent back, playing fully synchronized with the original message.
Samba was selected as a finalist for the SXSW 2014 Startup Accelerator competition. It plans to go live in the Apple Store "soon."
Here is a clip showing how to use Samba:
Here is an interview from SXSW 2014: