Amber!
Discussion
I don't want a signer though. I just want someone to securely store my nsec. From what I gather (after completing the onboarding) this will require me to approve events. I don't really want that.
Then I'd say a simple password manager, but I wouldn't put that on a device though
Better to use a "yubikey" of sorts. I know a few who are working on something kinda like that.
Most want it to also be a signer too.
The manual approval is a feature for more privacy minded users. You don't have to use it.
With Amber you don't have to manually approve each event sign.
You can assign permission to auto-approve certain event signatures.