The "Why Use JSMPEG" section hits the nail on the head with respect to the needs of some projects I have worked on.

Particularly, I once needed to stream video from a UAV to multiple tablets and phones on a local network to allow collaborative annotations. Since it was a disaster response system there was no depending on external services, which at the time put WebRTC out of the picture (all of the easy to use implementations required internet access to use existing signaling services).

We ended up using MJPEG and then later a JavaScript implementation of a MPEG-1 decoder. This library certainly would have made my life a little easier at the time!

See: https://github.com/cjb/serverless-webrtc

That's a good rough demo of how WebRTC connections can still be established with the ask/offers being conveyed out-of-band.

To make it a little more friendly for tablets (and to accomplish before messages expire) I'd think QR codes would be a reasonable way of passing the data without depending on an external service.

There could also be some extraneous information that can be stripped to save on the amount of data you pass between peers so that the QR code isn't excessively gross (see: https://webrtchacks.com/the-minimum-viable-sdp/)