I have something like this on my DW734 I use when planing thin stock. I don't use it instead of the stock tables and extra stock support (if required). With the stock tables adjusted high at the outer ends and physical control of the stock (controlled infeed and release at the outfeed) I get no snipe.
With a straight edge laid through the machine and resting on the outer edges of the tables, there is a gap of about 1/8" between the straight edge and the platen at the cutterhead position. This may seem excessive but at this point of adjustment, my snipe on boards 20"-plus in length, went away. Roller stands or other forms of support are required for longer stock, of course. This is just my experience, not a rule ;-)
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke