I think it is a really smart concept. Take the measurement feature of a TPM but remove the untrusted components supplying the measurements.
I really want one. I just currently don't know how to write device driver stuff and my ADHD means if I don't accomplish a project instantly I won't accomplish it at all.
Or download for free the CryptoServer SDK from https://utimaco.com/products/platform/cryptoserver-general-p... Their SDK contains a HSM simulator. They provide instructions how to run it in a container so that you then even have a network HSM.
Ease into it. We have fairly good documentation and some getting started material you can read (tillitis.se, dev.tillitis.se, GitHub) to gauge your level of understanding. The design is also meant to have the bare minimum complexity necessary to accomplish its functionality. It seems to have potential as a learning platform for college students who want to understand computers from the gates and up.