Heatmap.js is an open source JavaScript library that can be used for generating realtime heatmaps. It uses the power and flexibility of the HTML5 canvas element to draw heatmaps based on your data. Heatmap.js is an Open Source project dually licensed under the MIT license and the Beerware license. That basically means if you want to help improving the library go ahead, fork it and open a pull request on github.