Android app development (Read completely before you bid)

Android application (personal purpose- no need to publish in playstore) Purpose- 1.i have more than 10000 contacts- which i cant keep in phone contacts as it affects the performance 2. and i can not give all the numbers to my personal assistant who is a telecaller because of data safety 3.i want my telecaller to know only when he communicate with a number or search for a perticular number App is linked with one google account it will download all contacts from that google account and downloads in to phone as an encrypted file when ever there is an incoming call that app will show a popup with the contact name (like how the truecaller shows) user can also open the app and search for any number to see its contact name Features required it will auto update local file when ever contacts are modified in gmail account once installed it should have a login option- so that if any phone is lost, admin can disable his app remotely if not user login.. any other method also okay admin can change the gmail account if he needs i get more whatsapp messages than calls. so if it can show for whatsapp messages also.. will be very good. but not sure how to integrate with whatsapp... you try the best possible way for this purpose.