The advantages of the Grriper are that it 1) "bridges" the blade without contacting it so that everything is held and pushed through, 2) the rubberized bases give a firmer more stable grip to the work pieces, 3) when properly set up your hand cannot contact the blade, and 4) with two you have pretty complete control over all wood movement, and 5) you are both pushing and holding down the work pieces from multiple points if you use two. Using a single push stick of any design doesn't control the work piece on both sides of the blade. Doing that requires either two push sticks or one of your hands on the work piece.
Can you engineer or make something similar? Of course. Just like anything else.
If you use all the safety mechanisms on your table saw, the blade guard and pawls, then there's no particular advantage to the Grripper over any push stick or such since you won't be able to use the Grripper to hold down both sides of the cut. If you don't use a blade cover and pawls then the Grripper adds back a higher degree of safety over other types of push devices. If you are cutting panels or wider boards then it doesn't add much over other devices.
Where it really shines is cutting thin pieces where unsupported cuts can either get your unprotected hands too close to the blade or cutoffs can take flight.
It's not the answer to all types of cuts. What is? It is an effective safety device and I use mine quite a bit.