I am also deving a signing app. It support NIP-07 (Just like the app Spring) and NIP-46 (Remote Signing) for Android and IOS. And it also NIP-55 (Android local signing) for Android.
But it is under heavy develop, there are many things need to do.
https://video.nostr.build/6684ef4231be45d2bb09abfc5b15cf92fc600ceb1dfc27964f750c09e4aeea4f.mp4

https://image.nostr.build/14ea793612c9c0648f60a57f77b8d297037e272788e57f1091e5726c0a777946.jpg