Double tap to open favorite apps

So you want a launcher, but that only lists a subset of apps?

What you're after is very possible. As a start, you can actually just use the existing launcher code: https://github.com/espruino/BangleApps/blob/master/apps/launch/app.js

I recently added the ability to always run code at startup, so you could for instance add a file called favourite.boot.js and in it put:

(function() {
  var lastPress = 0;
  setWatch(function(e) {
    if (e.time-lastPress < 0.5) load("launch.app.js");
    lastPress = e.time;
  }, BTN1, {repeat:true});
}();

That'll load the launcher if you double-tap BTN1 (but will do it regardless of what app you're in, so you may need to be careful!).

You could then just make your own launcher...