The interesting article on smartphone Mass apps did not review the Roman Missal app which like Universalis, also uses the English/Australian readings at Mass.
Roman Missal is not the easiest to use, but is inexpensive (about $3.00) and comprehensive.
The Roman Missal app is principally designed for priests, as the celebrants' text is bold, while responses are in plain text.
It was created in collaboration with the publishers of the Roman Missal in English-speaking countries.
Roman Missal is dedicated to Pope Francis, contains the text of the Mass for the Pope, and prayers before and after Mass in English and Latin. It also contains the readings for a range of votive Masses, including Masses for saints, martyrs and the Blessed Virgin, as well as Requiem Masses and Masses for various needs and occasions.
The app can be used offline, unlike some other Missal apps that require an online connection to download the prayers or readings for the day.
Like other Missal apps, it has an implementation of the General Roman Calendar that automatically displays the celebration for the day for any day of any year. The app then loads the proper index pages for the respective season.
The app has handy buttons that correspond to the ribbon markers in the printed missal.
It does not have a trial period.