Video streaming among Android devices using Wi-Fi without Internet
Your best bet would probably be using a DLNA server app (This one, for example, though there are lots of others) on one device and an appropriate player (example) on the other devices.  Not sure if it would work over a hotspot tether though, but there are free apps available for both ends, so it can't really hurt to try.

EDIT: Oh, misunderstood the question. That's about as easy. There are several apps on the store for running a camera server, like this one, for example. You then can use any compatible player to connect and view the camera feed