A couple years ago I bought a universal windshield mount that will hold a cell phone or GPS that used a suction cup to stick to the windshield. On the suction cup was a clear gel substance that has the consistency of hair mousse, thick and tacky. As it never dries out, the suction cup only rarely looses the seal. Compared to similar devices I have used I would estimate this goo keeps a seal several times longer then an untreated suction cup; it is a great suction cup hack.
What is this stuff, the goo? What is it called, and are there brand names for it?