Pointer locks let an application lock the pointer position and receive relative motion events. As it concerns Phoronix readers, it's mostly important for gamers in correctly interpreting the mouse position when hitting the edge of the screen, namely first-person shooters. The Wayland pointer lock interface is modelled after the HTML5 pointer lock extension.
From the specific patch, "The extension allows a wayland client to lock the pointer while a surface is active. While the pointer is locked, the client receives relative motion events and the pointer position isn't updated."
Kristian proposed the core Wayland patches for the pointer lock extension plus implemented the support within Weston in this patch series. Kristian confirms that this feature should be useful for the Doom 3 Wayland port, the Wayland SDL2 back-end, and other cases.