Portable Ink by Takel and Titanas Magic
Item Number: TA8730
You draw a black dot on the back of a signed card and cause the dot to visually move by itself across the card. Your fingers are nowhere near the dot when it moves, and visibly slides across the surface of the card.
What makes this so visually stunning is that you can leave your hands and the card motionless as the black dot mysteriously glides from on side of the card to the other. It is easy to perform and easy to reset, and you can give out the signed card after each performance.
No magnets or unreliable mechanics. It works every time in every condition. Takes seconds to perform and will add a splash of visual magic to your next set.