I have seen these before and I have mixed results, Mostly negative. I think they are in the same catagory as the Pringle's can antenna. For a prosumer like us on this site I would say stick with an antenna that was designed for scanner with BNC connection.. http://www.cantenna.com/
The Slinky dipole has been around for a while, except now slinkys are made of plastic. I have a sneaky feeling they wouldn't work too well as an antenna, and I know for a fact they don't go down stairs as well as the metal ones did.