Hi Folks,
Wheelz, I think what you are recalling is a behavioral biometric tech commonly called “keyboard dynamics.” Wikipedia has a file on it as well as a list of 7 or 8 vendors who apparently market this technology, either as a single-factor authenticator, or as an element in a multi-factor authentication scheme, or as a factor used in a more complex “backroom” risk analysis that calculates the relative likelihood that the valid user is on the keyboard executing a particular transaction.
I recall that there were vendors (perhaps the same companies with different names) which offered versions of this tech back in the mid-1980s, but I suspect the algorithms they used then were not nearly as complex as those now used newer products. Unlike physical biometrics (like fingerprints, iris scans, or hand or facial geometry) behavioral biometrics offers not yea or nay, but a statistical probability that the habitual typing patterns of user X are those of valid user XY.
I, btw, loved the Angry Lurker’s complaint: “Seems to me that a ‘smart’ password which relies on rhythm would discriminate against those of us without any sense of that…” 
Keyboard dynamics is interesting, particularly as an element in a multi-layered risk assessment, but – despite the several commercial vendors Wikipedia listed – I’ve never run across it in the real world.
kferr nitpicked friedo when friedo referred to RSA’s SecurID as three-factor authentication. Although the classic SecurID implementation is indeed two-factor authentication – something known and something held – RSA has worked this space for a long time and today offers a very broad spectrum of SecurID hardware and software authentication options, at various costs, and with relative levels of robust security.
RSA, I believe, has only endorsed or licensed SecurID implementations with fingerprint biometrics – and only as a third factor of authentication, a complement to SecurID 2FA. (Lightning will strike me tomorrow if I overlooked some alternative biometric on RSA’s looooong list of SecurID partners.) There are, however, at least three vendors of fingerprint biometric readers for authentication which have integrated SecurID tech into their devices.
So, kferr, friedo was not completely wrong. Some SecurID implementations are indeed 3FA, although the classic 2FA mode is far more common. /end de-nit/
(For 3FA SecurID details, check out RSA’s documentation for the SecurID and Upek’s Secure Endpoint Solution, Prevaris’ plusID, and MXI Security’s “Remote Access”.)
I’ve been a consultant to RSA for decades, and my bias is overt, but if anyone has any specific questions, I’ll try to answer them. This is a great forum.