It could be camera wich would be thrown like Jarate or Milk, with that diffrence it stop moving after like 0.5-1 second (while in air), and becomes kinda like building wich have purpose by showing specific area to all teammates... just "placed" in air.
It could look always into direction it was thrown from (not random direction, because that would be then trash desing).
Throwing into wall would make it destroy before it starts working, wich then would make owner to wait until it recharges.
The view from camera would be avainable for all teammates on top of their actual view in the up-right corner (wich you can turn off at any time using special key), or make it item on another slot wich allow players to temporary swap screens with players and camera itself, and also in case of more than one player with this item - change camera you are looking from.

As for class it would be used, I think the best would be Engineer, but it would make a lot of sense to be used also by Spy. For both Engineer and Spy you could use this as second item slot (or maybe in case of spy even add it as another part of loadout just to buff Spies - they are preety bad in competetive comparible to Sniper, and swaping camera with sapper would make spy much worst vs Engineers).

When thrown at other player... it would crush on player dealing crushing 5 damage (or always crit for 15 - no one expect camera to be used as actual weapon).
I don't think seeing what other players do would be fair, altho giving up sapper for that ability maybe would be okay? What you think?

And of corse... camera itself would be destroyed easly by one bullet (give it like 1 HP), but it would also be small enouth to be hardly unnoticable if hidden in correct spot.
Throwing another camera while already having one working would cause old camera to be turn off.

What you guys think about this idea?