Teletia S
Looking up references for the Teletia S and went back to the official PGSM website archive. Now that I understand Japanese much, much better, I am fascinated by what the official description says.
Translation:
The communication items the Senshi holds are cell phone type, but they are special ones.
Except for Minako, the other four Senshi received their respective item from Luna. Whenever a Youma or other enemy appears, even if the phone is turned off, an emergency signal will still be triggered. As long as there is no direct interference from the Dark Kingdom, the Senshi can contact each other anytime, anywhere. The phone also has a function that allows the user to transform into any costume and appearance by taking a photo, and if the image is saved, the user can transform at any time! It seems that all the Senshi have various outfits saved in their respective phones should the need to use them arise Normally, they can enjoy making phone calls and sending messages as if they were normal cell phones.
I wrote AND rewrote EoT chapter 7 before finding this, so I feel a sense of validation for writing the phones to have operated on a "Senshi signal" based on some sort of "Lunarian communication system." lol
Also, I laughed at the part where they said the respective Senshi had saved up different costumes in their phone, though we know only Rei had saved up the practical ones based on Act 31. XD
Not sure what type of costume Makoto might have saved, but I'd bet Minako has the Sailor V costume saved in hers for a pseudo-transformation since that's how Artemis had her transform in Act Zero.
My specific headcanon about the Teletia S are:
They are waterproof.
They are shockproof and practically indestructible.
They don't need electricity to charge. Just by being near their owners, they are magically charged up.
^Basically it's completely made of alien / Lunarian technology
Emergency signal normally overrides silent/vibrate mode, airplane mode and being turned off. Artemis had to make some special adjustments for Minako's so hers doesn't ring in the middle of her work. Coz.... that'd be awkward.
The only downside of these phones is they look so childishly toy-like. The Senshi all kept theirs even as adults, but everyone but Rei also acquired a normal phone just coz... they got too embarrassed using their Teletia S publicly. Rei feels the same but is too frugal and doesn't use a cell phone enough to bother buying one. :P
Here's my theory/headcanon on how the physical Sailor V costume and Teletia S transformation work together.













