There are many ways to cope with the problems of yichud. One is not considered a “machmir” if steps are taken to prevent yichud, one is just following basic halacha. Whether or not a surveillance camera qualifies to block yichud is a shailoh addressed by contemporary poskim. Having an open door with the possibility that one may enter the premises without prior notification is clearly a better choice.
It is also poor judgment to conduct individual sessions at odd hours of the night when interruption is all but impossible. Even an open door is probably useless at such times, and halacha would prohibit the relationship altogether. Now, Cough Weberman Cough.