You don't have to use a toggle key like caps lock or num lock. When I used to use HKN, and now when I use ISBoxer, I made "home" turn broadcasting on and "end" turn it off. That way I can spam a key and not worry which toggle state it's in. For example, if I have key broadcasting turned off and am typing in a BG and some silly horde jumps the lolsmite priests of doom, I know I can hit my home key and start holy novaing away until the dance party begins.