I know this one is going to sound weird but hear me out.

I have a heart rate monitor that is hooked up like a keyboard to the computer. Each time the heart rate monitor detects a pulse it sends a key stroke.

This keystroke is then detected by a web based game running in the browser.

Currently I'm sending the following keystroke: (`)

In the browser base game I'm detecting the following key fine and if when the user is on any data input screens the (`) character is ignored using a bit of JavaScript.

The problem comes when I leave the browser and go back to using the Operating system in other ways the (`) starts appearing everywhere.

So my question is:

Is there a key that can be sent via the keyboard that is detectable in the browser but wont have any notable output on the screen if I switch to other applications.

I'm kind of looking for a null key. A key that is detectable in the browser but has no effect to the browser or any other system application if pressed.