The idea seems to be quiet old …
“All the same, technical difficulties abound in making the technology work as promised and a half-dozen efforts at commercial technology have failed. Differences in the physical characteristics of keyboards, even of the same brand, and communications protocol stmctures are thorny hurdles for developers.”
https://archive.org/details/ieee-spectrum-1994-02/page/29/mode/1up
… and some quiet knowledgeable people seem to not consider it successful nowadays neither:
“Other systems
Many other biometric technologies have been proposed [1315]. Typing patterns,
were used in products in the 1980s but don’t appear to have been successful…”
Ross Anderson, “Security Engineering” v3 Sep7, Chapter 17.7, p540
If you really care in spite of this information you should get yourself something like:
https://shop.mntmn.com/products/mnt-reform-usb-keyboard-standalone
Then you can tinker with the firmware and add some random delays to keystrokes:
Maybe @mntmn@mastodon.social likes the idea of doing something like that and will add that feature by themself 
.