http://9to5mac.com/2015/04/29/pixelmator-for-mac-adds-force-touch-pressure-sensitive-painting-even-better-repair-tool-more/:
Pixelmator brushes now support Force Touch so you can draw with multiple levels of pressure by pressing harder on the touchpad of your new Retina MacBook (or early 2015 13 inch Retina MacBook Pro). This is useful for quick adjustments although serious painters will still want to use dedicated drawing tablets. This is a perfect example of how Force Touch is going be a great new way to interact with apps. I wish I could access Force Touch at a detailed level on the Apple Watch for our new games.