I just listened to it and it was really interesting, for me especially in regard to the particular uses and qualities of visual data as proof.
It made me also think about the fact that even if you produce a photographed testimony, whether by using a hand held device or with a kite as proxy, you still need to defend and authenticate the validity of the information, by testifying in person and authenticating the process, as mentioned by Edan and Aaron, but also you might also need to authenticate metadata for proving the reliability of you visual data - especially in the case of photographs which can be easily manipulated.
It reminded me of this app, CameraV, for android phones that lets you take pictures/video while encrypting a lot of metadata and sending it to a secured destination. Another form of witnessing through proxy.
might be relevant to some of you.
hagit.