This answer is based on my answer to the old question What sci-fi work introduced handheld wireless communicators?. A pocket telephone from 1915 and a pocket videophone from 1930, no mention of touchscreens.
1915: a wireless pocket telephone without video.
"John Jones's Dollar", a short story by Harry Stephen Keeler; first published in the August, 1915 issue of The Black Cat, a scan of which is available at the Internet Archive; the text of the story is also available at Project Gutenberg. In the excerpt below, a professor is teaching a kind of Zoom class:
"B262H72476Male, you are late to class again. What excuse have you to offer today?"
From the hollow cylinder emanated a shrill voice, while the lips of the picture on the glass square moved in unison with the words:
"Professor, you will perceive by consulting your class book, that I have recently taken up my residence near the North Pole. For some reason, wireless communication between the Central Energy Station and all points north of 89 degrees was cut off a while ago, on account of which fact I could not appear in the Visaphone. Hence—"
"Enough, sir," roared the professor. "Always ready with an excuse, B262H72476Male. I shall immediately investigate your tale."
From his coat pocket, the professor withdrew an instrument which, although supplied with an earpiece and a mouthpiece, had no wires whatever attached. Raising it to his lips, he spoke:
"Hello. Central Energy Station, please." A pause ensued. "Central Energy Station? This is the professor of history at the University of Terra, speaking. One of my students informs me that the North Pole region was out of communication with the Visaphone System this morning. Is that statement true? I would—"
A voice, apparently from nowhere, spoke into the professor's ear. "Quite true, Professor. A train of our ether waves accidently fell into parallelism with a train of waves from the Venus Substation. By the most peculiar mischance, the two trains happened to be displaced, with reference to each other, one half of a wave length, with the unfortunate result that the negative points of one coincided with the positive points of maximum amplitude of the other. Hence the two wave trains nullified each other and communication ceased for one hundred and eighty-five seconds—until the earth had revolved far enough to throw them out of parallelism."
"Ah! Thank you," replied the professor. He dropped his instrument into his coat pocket and gazed in the direction of the glass square whose image had so aroused his ire. "I apologize, B262H72476Male, for my suspicions as to your veracity—but I had in mind several former experiences." He shook a warning forefinger. "I will now resume my talk."
1930: a wireless pocket videophone.
"Mr. Murphy of New York", a short story by Thomas McMorrow; first published in the March 22, 1930 issue of The Saturday Evening Post, available at the Internet Archive.
"Now, gentlemen, please," breathed Mr. Bligh. "Do remember that I'm a thousand miles from home and haven't had any lunch yet. Well, I shall have to call up." He took out his pocketell. "Are you there? Billy calling . . . Hello, Molly! I just called you to say that I can't possibly get home— What's that, sweetheart? . . . Oh, no, no. . . . But I say that I am not! I am in New York in a conference. . . . Yes, business. . . . Why don't I— Now, Molly, how can you ask me to be so rude? . . . Oh, very well, my dear, in a moment." He turned to us, coloring, and said, "Will you permit?" We were married men ourselves; we smiled and got to our feet and bowed to his lady when she appeared; her eyes swept us vigilantly. "I'm sorry this had to happen, gentlemen," said Mr. Bligh, blanking her. "May we proceed now with our affair?"