Can I run a user test with Lookback through the mobile app?

Lookback is no longer available on iOS and is only available on desktop and mobile devices with a custom share link. For more information on user testing options on iOS, view our announcement here. 

Lookback does make available an Android app for using their service that may be of help, but it's not specific to InVision.
The InVision iOS app also lets you view screens from Apple Watch prototypes on an actual Apple Watch. However, the screens are not interactive and you can only swipe left and right to switch screens.