Originally released in Japan on August 24, 2017, Prisma Illya Alarm: Magical Ruby Selection Illya has been announced for an English release in early May 2018. 
The app features Illyasviel von Einzbern who stars in the Fate spinoff series, Fate/kaleid liner. The app contains over 250 new voice recordings by voice actress Mai Kadowaki, and 30 illustrations drawn by the anime studio Silver Link.

 Probably the most exciting feature at an additional cost, fans can now sleep with Illya in Sleep Mode which adds 40 new voice recordings including breathing sounds.
The original app sold for 960 yen on Google Play and the App Store, and currently no pricing information has been announced yet for the English release.

To learn more, please visit the official homepage:
http://prisma-illya-alarm.d-techno.jp/index_en.html