Google Duo: Simple, encrypted, video calling app
All Duo calls are end-to-end encrypted, and naturally, the video resolution quality will depend on the speed of your connection. Duo can switch between Wi-Fi and cellular data automatically without dropping your call.
A simple, yet interesting feature is KnockKnock, which lets you see live video of your caller before you answer, giving you a sense of what they’re up to before you pick up.
iOS users already largely use FaceTime, but this app would make it easier to call those on the contact list that are not on the same platform.