It's no longer common practice to have halachic decisors permit the use of electricity. And while there may have been many decisors in the past that allowed the use of electricty, most of them are from 30+ years ago, describing things like the use of lightbulbs, microwaves, etc so i would not dare to claim how they might answer regarding a smart phone since they would have never seen one in their lifetime. But here is a list of every Rabbi that i'm aware of that allowed the use of electricity on Yom Tov, and you can go ahead and read their responsa to decide if any of them might apply to your question.
1903 Rabbi Yechiel Michel Epstein (the author of the Aruch Hashulchan)
in Bet Va'ad LeHakhamim allows turning lights on on Yom Tob.
1903 Rabbi Yosef Yehoudah Strazberg (author of Yad Yosef, & Ab Bet Din
of Makasov, Galitzia) in Bet Va'ad LeHakhamim also allows turning them
on.
1912 Rabbi Refael Aharon Ben Shim'on (Chief Rabbi of Egypt) (He wrote
this in 1901) in his UMitzor Debash allows turning them on.
1913 Rabbi Binyamin Aryeh HaKohen Weiss in his Eben Yeqarah allows
turning them on.
1924 Rabbi Yehuda Yudil Rozenberg in his Maor HaHashmal in Montreal,
Canada allows turning them on.
1932 Rabbi Ruben Margaliot in his Nefesh Hayah allows turning them on.
1934 Rabbi Yosef Messas (Rabbi of Tlemcen, Algeria and Meknes, Morocco
and Haifa, Israel) in his Mayim Hayim allows turning them both on and
off and he reiterated his position in numerous other places.
1934/35 Rabbi Tzvi Pesach Frank (Chief Rabbi of Jerusalem) in Qol Torah
allows turning them on.
1935 Rabbi Ben Sion Meir Hai Uziel (The Rishon LeSion himself) in his
Mishpete Uziel allows both turning them on and off and he reiterated
this in 1947.
1936 Rabbi David HaKohen Saqli (Rosh Ab Bet Din in Oran, Algeria) in
his Qiryat Hanah David (volume 2) allows both turning them on and off.
1945 Rabbi Eliezer Yehoudah Waldenberg in his famous Tzitz Eliezer
(volume 1) allows turning them on.
1948 Rabbi Masoud HaKohen in his Pirhe Kehounah (Casablanca) allows
turning them on.
1964 Rabbi Shraga Faivel Frank in his Toldot Ze-eb allows turning them
on.
1973 Rabbi Shabetai Sheftel Weiss in his Hilkhita Rabeta LaShabeta
allows turning them on.
Source: List compiled by Joseph Mosseri.