Also check out nostr:nprofile1qqswacu3amp428kj8wtpqf77yd2upukcn2ft4aycmxm5scmh359e0ssppemhxue69uhkummn9ekx7mp0qyg8wumn8ghj7mn0wd68ytnddakj7qg4waehxw309aex2mrp0yhxgctdw4eju6t09uvt9vcv and nostr:nprofile1qqs83nn04fezvsu89p8xg7axjwye2u67errat3dx2um725fs7qnrqlgzqtdq0

Amber is a signer app on your mobile (like the chrome extension you tried out) where you can store your nsec and login to your mobile nostr clients without entering your nsec into them.

Zapstore is a Nostr-integrated app store from which you can download APK's which are signed and verified by the devs themselves.