Introducing a smartphone protection case with an integrated headphone, literally a single earpiece to take a minimum of volume, speed up the connection (* 1) to the biological hearing device and keep the other ear available for our immediate physical environment. Of course the aesthetics of this prototype is debatable, but it works admirably well and will hopefully allow the author to avoid long-term micro-waved neuronal damage (* 2). What about commercial products? A nice surprise the integrated headphone market for smartphones is very interesting, first of all of course for cutting edge smartphones some of which have automatic cord unwinders, which appear as very practical. The precautionary principle in personal mobile telephony tends to grow so this kind of devices are likely to become widespread. If you can't find a decent smartphone case with built-in earphones you can of course make one yourself, here are the steps I used to build the one pictured just beside, with an old glasses case used as a "pocket" storage for the earpiece and glued in the appropriate position on the smartphone original removable shock protection case. Steps taken:

1. Find a glasses case or another object with appropriate dimensions.
2. Shorten it with scissors so it can fit on the smartphone case. Beware of seams, it's necessary to strengthen the parts having undergone cutting.
3. Punching holes in the case is optional but allows a better perception of the condition of the cord inside the case while increasing its internal friction capacity.
4. Separate the smartphone protection from the smartphone (the protection will be reassembled on the smartphone once the work is done and the glue evaporated).
5. Glue the protection to the correct place using rubber contact glue, which involves coating a thin film on both surfaces to be glued and then allowing them to dry for a few minutes (the appearance of the glue in the air must be almost dry) before assembling them definitively.
6. Wait a few hours for the last smells of glue to disappear.
7. Here it is done and depending on the models and the available space we can leave the jack of the earphone connected or not. Note that the "folding" that seems most practical is to stuff the "bag" in small segments of a dozen centimeters.

(* 1) In practice we save much more than a factor two, because with two headphones and a smartphone usually held in the hand, the grip of the first earpiece hopefully is done directly, but the second usually hangs in a random manner which increases the time of identification, grab and insertion. It is also this irresistible hanging coupled with the gigantic and bouncy character of the pictured headphone (he had a twin shortly before the photo) that made me think of a clackers toy, by the way it was possible to make the basic tac-tac movements with these earphones in their original shape.

(* 2) I previously counted on the speaker of the smartphone, but the distance is less than what you get with earphones and of course it's harder to maintain.