Every Step You Make: Can One Wear Smart Jewelry With Safety Features On Shabbat?

Graphic depicting violence targeted at women above age 16 and the physical locations. (Source: German Police)

What could be the safety concerns?
Are there additional concerns for Jews? If so, of what nature? If not, how so?
Wearables:

"are smart electronic devices that are worn close to and/or on the surface of the skin, where they detect, analyze, and transmit information concerning e.g. body signals such as vital signs, and/or ambient data and which allow in some cases immediate biofeedback to the wearer."
The Case of The Nimb Ring:

As a result of having been violently attacked while walking down the street, Nimb’s CEO and co-founder Kathy Roma decided to found a company that would work towards providing greater personal security. Therefore, Roma converged a group of developers to work towards her goal. As a result, Roma and colleagues developed “Nimb – a smart safety ring”.
The development of this ring reflects a trend in Hi-Tech industry: The development of wearables. Those appliances are “hands-free gadgets with practical uses, powered by microprocessors and enhanced with the ability to send and receive data via the internet” (Kenton, 2019).
The Nimb-ring:
Integrated ready-to-connect cellular module provides global coverage & cloud management
Able to send an alert to trusted contacts and/or emergency responders instantly - helps the wearer to escape an unsafe situation quicker.
Operating the device: the wearer simply presses a button that is so discreetly hidden, that it is hardly visible to whoever is unacquainted with the device. This quick and user-friendly function is facilitated by a sophisticated technological system

Is the glass half full or half empty: A question on perspective on the Halachic concerns regarding the Nimb Ring
Muktzeh
מַתְנִי׳ לֹא יֵצֵא הָאִישׁ לֹא בְּסַיִיף וְלֹא בְּקֶשֶׁת וְלֹא בִּתְרִיס וְלֹא בְּאַלָּה וְלֹא בְּרוֹמַח. וְאִם יָצָא — חַיָּיב חַטָּאת.
MISHNA: Just as it is prohibited for a woman to carry out certain items unique to a woman into the public domain, the Sages said that a man may neither go out on Shabbat with a sword, nor with a bow, nor with a shield [teris], nor with an alla, nor with a spear. And if he unwittingly went out with one of these weapons to the public domain he is liable to bring a sin-offering.

דברים המותרים והאסורים לטלטל בשבת ובו נב"ס:
כל הכלים נטלים בשבת חוץ ממוקצה מחמת חסרון […] כיון שמקפידים שלא לעשות בהם תשמיש אחר אסור לטלטלו בשבת ואפי' לצורך מקומו או לצורך גופו:

Objects that may or may not be carried on Shabbat
All implements are carried on Shabbat except for implements that are muktze [=set aside] because of monetary loss […] Since one shows great care not to use those for any other purpose, it is forbidden to move them on Shabbat, even for the "purpose of its place" (=its place is needed), or for the "purpose of the object itself".

Writing on Shabbat
"The key part of the smartwatch is the digital chip on which computer operations are processed and results are recorded. If we are to answer the question whether one may wear a smartwatch on Shabbat, given that it will make digital recordings of his/her health, understanding the functionality of the digital chip is critical.
Among the halakhically challenging and complex issues in contemporary technology is the digital refrigerator. These refrigerators have a computer chip that records the temperature, when and how long the door is open, and computes calculations regarding when a defrost is necessary. Although resolving the various questions involved with using such a refrigerator on Shabbat is beyond the scope of this article, there are two approaches with respect to the digital recordings of the computer chip that further our above analysis.
Many poskim permit causing the computer chip to make these recordings. This is because one does not really care that they are recorded, as the refrigerator could just as well work on a periodic schedule of defrost (although with less energy efficiency). In technical terms, this adds up to a pesik reisha de-lo niha leih of a rabbinic restriction of using electricity, which results in it being permitted, as described in the previous section. This assumes that there is no prohibition of kotev in having the information recorded in a computer chip, since it is not considered writing in any intelligible language. Alternatively, if one assumes that the concern about recording is makeh be-patish, it could be permitted according to a position of the Maggid Mishnah (Hilkhot Shabbat 12:2) that it is only possible to violate makeh be-patish while intentionally trying to create a utensil. An unintentional creation of a “utensil,” as in our case, is not considered the creation of a “utensil” at all.
[…] Rav Heinemann (cited in Or ha-Shabbat ibid.) holds that a melakhah is defined by something which has a tangible result that can be perceived with one of the five senses. Since the results of the computer chip are unintentional and unobservable to any human being, they are completely insignificant halakhically and do not violate the prohibition of using electricity on Shabbat. Furthermore, if one assumes that the issue with electricity is makeh be-patish, it is permitted since the result of the actions is unobservable and thus halakhically inconsequential."
From: https://thelehrhaus.com/scholarship/wearing-a-smartwatch-on-shabbat/

A case for self-defense
הַבָּא בַּמַּחְתֶּרֶת בֵּין בַּיּוֹם בֵּין בַּלַּיְלָה אֵין לוֹ דָּמִים אֶלָּא אִם הֲרָגוֹ בַּעַל הַבַּיִת אוֹ שְׁאָר הָאָדָם פְּטוּרִין. וּרְשׁוּת יֵשׁ לַכּל לְהָרְגוֹ בֵּין בְּחל בֵּין בְּשַׁבָּת בְּכָל מִיתָה שֶׁיְּכוֹלִין לַהֲמִיתוֹ שֶׁנֶּאֱמַר (שמות כב א) "אֵין לוֹ דָּמִים":
Safek Pikuach Nefesh
וכבר היה ר' ישמעאל ורבי עקיבא ורבי אלעזר בן עזריה מהלכין בדרך ולוי הסדר ורבי ישמעאל בנו של רבי אלעזר בן עזריה מהלכין אחריהן נשאלה שאלה זו בפניהם מניין לפקוח נפש שדוחה את השבת
§ The Gemara relates: It once happened that Rabbi Yishmael, and Rabbi Akiva, and Rabbi Elazar ben Azarya were walking on the road, and Levi HaSadar and Rabbi Yishmael, son of Rabbi Elazar ben Azarya, were walking respectfully behind them, since they were younger and did not walk alongside their teachers. This question was asked before them: From where is it derived that saving a life overrides Shabbat?
נענה ר' ישמעאל ואמר (שמות כב, א) אם במחתרת ימצא הגנב ומה זה שספק על ממון בא ספק על נפשות בא ושפיכות דמים מטמא את הארץ וגורם לשכינה שתסתלק מישראל ניתן להצילו בנפשו ק"ו לפקוח נפש שדוחה את השבת
Rabbi Yishmael answered and said that it is stated: “If a thief be found breaking in and be struck so that he dies, there shall be no blood-guiltiness for him” (Exodus 22:1). Now, if this is true for the thief, where there is uncertainty whether he comes to take money or to take lives, and it is known that bloodshed renders the land impure, since it is stated about a murderer: “And you shall not defile the land” (Numbers 35:34), and it causes the Divine Presence to depart from the Jewish people, as the verse continues: “In the midst of which I dwell, for I the Lord dwell in the midst of the children of Israel” (Numbers 35:34), and even so the home owner is permitted to save himself at the cost of the thief’s life, then a fortiori saving a life overrides Shabbat.