Planning Poker6 is a similar technique, but it involves cards. There are many popular Planning Poker card decks out there. Most use some kind of Fibonacci series. One popular deck contains the cards: ?, 0, ½, 1, 2, 3, 5, 8, 13, 20, 40, 100, and ∞. If you use such a deck, my advice to you would be to remove most of those cards.
