Keep is a FROST threshold signing app and dedicated Nostr event signer for Android. It allows users to hold FROST key shares on their phone and sign Nostr events without any single device ever holding the full private key.

https://zapstore.dev/apps/naddr1qvzqqqr7pvpzp43w35zzuz82rhvvy25c09ypvykewfqms5hlrvsv52vr6ftflfuuqqtkjmewwpexjantv4uju6m9v4czuctwv3ex76tyq3quu5