Overview
Your mouse and keyboard activity will be tracked independently for each game, allowing you to render high quality images in any colours. All resolutions are recorded separately and merged when generating the images, so lowering or raising your in game resolution won't cause any problems.
The idea came about from the Razer Synapse tracking, as it does not cope well with extended use or resolution changes.
It does however do a good job with the keyboard and click heatmaps, and was used for inspiration for this.
Mouse Movement
Track everywhere the mouse moves, and fade out the older tracks.
Mouse Clicks
Record every click ever made, and show it on a heatmap. You may choose to hide a particular mouse button, for example if it is only ever used for moving the camera.
Keystrokes
Draw a keyboard with colour coded keys, based on number of keystrokes, or the time spent being pressed. This does not act as a keylogger, so you are still safe typing passwords.
Unfortunately this doesn't work on anything related to Steam.