There's an annual tournament in Texas - can't remember the name, it's held at Lake Conroe outside of Houston, made up of pros from the FLW and Elite series. The lake has a 1 fish only regulation and it's a slot limit, so if they get one that's in the slot they'll keep it to show at the weigh-in, but all others are weighed and released. They have a marshal on board that verifies the weight with the pro. Since the tourney is televised they have some video on some of the boats, but it is not there as a weight verification tool.
The format seems to work well, and I don' see why it could not be used on the bigger tournaments where you have plenty of volunteers to be marshals.