Hi,
It's funny, I just posted this idea for another KOP user, and I think it may be something you could use also!
The idea is collar that contains compressed air - the owner has a remote, where when the dogs behaviour starts to do it's bad behaviour, you blast the dog with a little jet of air. There are three-four settings on the remote for different levels of behaviour problem (the more excited the higher the pressure).
The collar is nice, as it isn't an electric shock collar - it's just air. It works on the principle of surprising the dog before the behaviour has a chance to escalate - allowing you the time to reprimand and correct the behaviour with a command like sit-stay, heel, or down-stay.
When using something like this, make sure you read the instructions thoroughly before applying the techniques. Like usually you are required to have the dog wear the collar for a week or so before using it to reprimand, so the dog doesn't associate the collar with the reprimand - this is so that if you take the collar off - the dog will still listen to you!
The nice thing also is that the dog isn't going to associate the reprimand of the collar directly to you, the way a spray bottle is associated. So no fear of the dog becoming immune to it, or fearful of you.
Not the same as the one I saw, but similar in concept is this product:
Multivet Spray Commander remote trainer spray collar
Blue