Inklet allows your trackpad to emulate a pen tablet. When you're using a Pogo Sketch, the trackpad even becomes pressure sensitive.

Features:

The full tablet

Moving your Pogo Sketch lightly around the trackpad will allow the cursor to hover without inking. Increase pressure to draw; heavier pressure will result in a thicker stroke.

Handwriting recognition

Inklet works with the handwriting recognition built into OS X. Use your trackpad to jot notes or doodle.

Advanced palm rejection

Inklet includes an advanced algorithm to detect unwanted trackpad touches. This means you don't have to worry about accidentally resting your palm on the trackpad as you draw.

Requires OSX 10.7 or later

Home Page - https://tenonedesign.com/inklet.php