This article contains plot/ending details.
Lynette Guycott has an artificial right arm called a Bionic Arm. The exact reason for why she had her real right arm replaced is unknown, though a possible explanation might be to increase her drumming abilities. Her bionic arm is extendable, allowing her to attack from a long distance. The arm is also quite powerful; one hit from it was enough knock the highlights out of Knives Chau's hair.
In Scott Pilgrim vs. the World: The Game
In the video game, a Bionic Arm can be purchased at Wallace's Mystery Shop for $129.95. It will give the player a +50 Strength bonus.