Good idea but not really new. The old guys here will remember them from long ago. Maybe back as far as the 50s > http://www.jcwhitney.com/exhaust-cut...?filterid=u0j5
The problem was they'd get stuck if you didn't use them every day and keep them lubricated with something that could take the heat. You'll also want to watch your spark plug color to tell you if you're running too lean.