I don’t really understand why you’d want to do this, but I don’t really understand a lot of that whole “body modification” kind of thing to begin with. At least this is totally temporary. In the video below, you can see Noda Akira showing off his latest creation: a blue LED that you stick up your nostril and it will respond to your breathing by lighting up.
The demonstration has the little electronic device being shoved up a nostril, but it could theoretically work under a number of different circumstances too. It’s designed to sense a draft (like your breathing), pulsing its light in response. I think it might be useful for detecting a drafty window.
Toward the end of the embedded video below, you’ll also see Akira showing off another creation: the HeartCap mini. Again working with an LED light (yellow this time), this presumably senses your heart beating and pulses its light rhythmically in time with your old ticker.