GPS clock_info - a few questions

is this var timeout the same variable as this.timeout

Nope :)

I'm not 100% sure I understand how this.timeout gets defined in code at:

It's defined in .run just a few lines earlier: https://github.com/espruino/BangleApps/blob/master/apps/clock_info/lib.js#L83

run : function() {
        Bangle.setHRMPower(1,"clkinfo");
        if (settings.hrmOn==1/*Tap*/) {
          /* turn off after 1 minute. If Health HRM monitoring is
          enabled we will still get HRM events every so often */
          this.timeout = setTimeout(function() {
            this.timeout = undefined;
            Bangle.setHRMPower(0,"clkinfo");
          }, 60000);
        }
      },