Stihl laser sighting and measuring guide

[SimonFisher]

Just found this:-

http://www.youtube.com/watch?v=pelw_bbwRYU

Even in an animation, they show the chain break being applied and released

Anyone seen or used one?

[Dexter's Shed]

looks like a lot of faffing about, although will appeal to blokes that like gadgets
maybe I should ask my Chinese friends if they make/copy simular