The Spyglass's anti-AFK feature will prevent your avatar from showing that you are away from your keyboard. It will also help keeping you logged in (no logouts for inactivity).
To turn anti-AFK on or off, open the menu by clicking the "Menu" button, then go to Tools. Clicking the Anti-AFK button will switch anti-AFK on or off. The current state is shown in the dialog and in local chat.
Anti-AFK won't stop working if you power off your Spyglass.