Boo.js is a library that runs a function when a user is inactive. It's used in Mojo.js to warm-up views asynchronously before they're used.
Example: http://jsfiddle.net/G56uE/4/
var boo = ; // run this function every N MSboo; // run this function when a user is inactiveboo; // trigger wait for 1 secondboo;