Basically:
Can you leave your computer with video chat on (to another person) on over shabbos? And what if there's also audio?
For example a relative in the hospital, relatives that in a far away country, or just on in general.
This is all under the assumption that you will not touch the computer or camera.
The answer to Can one run a surveillance Camera on Shabbos? quotes Dose of Halacha as saying, with regards to being photographed by a surveillance camera:
R’ Moshe Feinstein (in a letter to R’ Yisroel Rozen of the Tzomet Institute) wrote that as the data is not being permanently recorded, it is at worst a derabanan. Although the cameras operate for security purposes, the passerby does not benefit from being photographed. One only benefits from the system when there’s an unwelcome intruder. Thus, one may walk in front of a camera on Shabbos as this is a case of pesik reisha delo nicha lei (see Shulchan Aruch OC 320:18) which is permitted in a rabbinic prohibition. Likewise, one may operate a surveillance camera. R’ Shlomo Zalman Auerbach (quoted in Ateres Shlomo 6, p57) concurs.
In the passage i bolded, we see that the reason Rav Moshe allowed it is that it is a psik reisha d'lo neicha lei -- an unavoidable melacha that he does not benefit from.
This is not the case by a video chat. Here, the person being videoed definitely does benefit from it -- that's the whole point of leaving it on. Hence, it must be a case of psik reisha d'neicha lei (an unavoidable melacha whose outcome is favorable to him) which is forbidden.
You may want to view these other discussions:
Why do music tapes and CDs warn about playing on Shabbos?
Am I allowed to view a Kotel Cam on Shabbos?
In terms of an answer: It seems to me that this would be the same as viewing television on Shabbat, being not in the spirit of Shabbat, even when left on. However, I wonder if it falls under medical necessity in terms of hooking up to someone in the hospital. I would extend the question further to: is it okay to video chat with a Doctor on shabbat, in the event of an emergency. Does this break fewer laws than answering the phone, if the entire computer and video chat are connected before Shabbat?
This seems that it would be asur (Yalkut Yosef Kitzur S"A 318:51-53). A paraphrase:
יש ללמד לא להכניס לתוך סרט וידיאו לפני שבת עבור המכשיר לעבודה על ידי קוצב זמן.
It is [proper] to teach to not put a movie into a vcr before shabbat and for the device to work by a timer.
Rabbi Herschel Schachter explains that this is only in a definite pikuach nefesh situation.
If the government or a physician has decided that an individual must remain in isolation over the course of Yom Tov and this individual has a psychological condition where physicians who know this patient have determined that there is a possibility that this person being alone over the course of Yom Tov would be in a situation of pikuach nefesh (possible suicide) if the individual was not able to communicate or speak with family members, then the family members must reach out to this person over Yom Tov to speak on the phone or use the internet by leaving a connection open from before Yom Tov. Rav Moshe Feinstein has decided that, in certain circumstances, psychological danger is considered life threatening. Rabbi Soloveitchik went further and noted, in the name of his grandfather Rav Chaim Soloveitchik, that even if there is a concern that someone will lose his or her mind even if their life is not in danger, that too is considered a case of Pikuach Nefashos.
If a person is physically ill and alone and the physicians have determined that there is a possibility of the condition deteriorating further to a point of being life threatening, then the family must remain in contact using electronic devices with that person over the course of Yom Tov in order to check on the person's well being.
Additionally he says
However, to leave a computer screen on and to have people watch and connect over the internet is a greater concern of violating Shabbos and Yom Tov since it creates images and pictures when the people move.
In light of the COVID-19 (Coronavirus) pandemic, a group of Sephardi senior Orthodox rabbis have permitted Zoom [video conferencing] for use during this year's Passover Seder (and only this year's Passover Seder), providing the video conference is established prior to the holiday beginning:
English news sources:
Unsurprisingly, this triggered immediately controversy with reports of one or more of the rabbis subsequently retracting the ruling.
