Not very useful. Mobile apps are pretty trivial to clone (clone poorly, usually), and anything remotely successfully is cloned within days of popping up on the radar.
The first-mover advantage is close to zero. The lone exception are things that are intrinsically hard to clone - deep hardware-level integration, native code that stretches the limits of current platform understanding, etc.
Which doesn't apply at all to webview-powered apps. At all.