Inverse timers and smell based timers

In an intro class to zen meditation they mentioned that incense was used to time meditation in the past. I found this interesting, first of all because it is a smell based timer, and I'd only thought about sound based timers before.

Secondly because it is a timer that stops giving signal when it is done. We use inverse timers in some settings, but often when the time is short and we want to increase tension, for example in a game where you have a fixed amount of time or in a game show, and it is often paired with a loud signal at the end as well, not no signal as would be the case for the incense.

I think timers like this sound nice for activities where the times running out does not mean an immediate action has to be taken. Like when meditating or doing a pomodoro timer while working. When the timer stops making sound you know you've done the time you wanted but you don't have to get up or stop the activity to turn off the timer, and there is no sharp noise to shake you out of focus.

Smell timers I don't know about, there must be other settings than meditation they can be useful for?