From Rabbi Moshe Heinemann:
Riding to the Hospital
A woman need not spend Shabbos/Yom Tov at a location close to the hospital or arrive at the hospital before labor starts to avoid riding on Shabbos/Yom Tov. The order of preference in arranging transportation for an expectant mother is as follows:
A. 1st - Pre-arrange with a non-Jew.
B. 2nd - Use a taxi service. (When phoning for a taxi, one should not reveal that a woman is in labor. Some taxi drivers hesitate to transport a woman in labor to the hospital. This is a suggestion, not a Halacha.)
C. 3rd - Have a Jew drive the pregnant woman. The Jew should drive normally, e.g. using signals, brakes, lights, etc. The Jew should drive in the usual manner because if he chooses to perform fewer Melachos, he might cause an accident.
My question is, pertaining to B, would using the Uber app be preferable to calling on a regular old fashioned telephone and using a taxi service? Is using the app doing less or more Melacha?