Find My Phone app allows you to locate family members or your lost device from any device (Android, Apple, Laptops etc) through WhatsApp
With the app you can create a message trigger that will send back the last location of your lost device back to you through WhatsApp and show you the location on the map (google maps).
First you create a message trigger from the main screen and whenever your lost device will receive that message through WhatsApp it will reply with a url that shows you the location of your lost device in google maps.
It's so simple that you will be amazed!
Available in Google Play for free: Google Play Link