- certificate management amongst a plethora of hosts, both SSL/web certificates for external use, and management and installation of self-signed "root" certs for validating internal applications and services - keymastering server: an appliance that acts as a genuine root of trust for an organization, using a Yubico HSM for key storage, but providing middleware & admin controls to manage issuance and distribution of intermediate certificates - AD/LDAP/SSO/etc user management, key issuance, etc.
If you have a small team and you don't need global redundancy for these functions across a large fleet, then it makes a lot of sense IMO to shell out $5-10k for a set it and forget it security appliance that makes certificate/key management simple and easy.
I think the biggest challenge is that it's hard to build trust as a startup without open-sourcing your stack, but that makes it a lot harder to get buy-in for an appliance model unless you have some creative dual-licensing ideas.
But "your keys/certs are stored securely on your hardware in the room next door" is a compelling value proposition & probably a much easier pill to swallow for certain companies than a cloud HSM or other solutions which sorta boil down to "trust me bro".