As mentioned before, I was able to read the German-language book on electronic levels well enough to tell that the book wasn't that helpful, and that the authors did not understand how these levels worked.
However, the book did have two or three references, also in German. So I googled them down, which led me to an article by a German engineer (now Diplom Ing) who had in effect combined the Taylvel and Wyler approaches, yielding a far simpler unit.
The relevant article is "Hochpräzise Neigungsmessung mit dem elektronischen Einachspendelsystem HRTM" by Timo Kahlmann (ETH Zürich), Christian Hirt (Universität Hannover), and Hilmar Ingensand (ETH Zürich), Ingenieurvermessung 2004, 14th International Conference on Engineering Surveying Zürich, 15. 19. März 2004.
Even if you don't read any German, the figures and photos tell the story.
Some details:
The pendulum hangs on two 50-micron thick (0.002") by 3mm (0.118") wide bits of metal foil. The figure implies that the foil is made of spring steel (Federstahl) leafs (Blattfedern) but the text says that they are made of beryllium-copper foil. Brass shim stock or stainless steel foil should work, or some feeler gage stock.
Pendulum swing is limited by two nylon screws (Arrierschraube, Kunststoff).
While a Talyvel-like pendulum is used, the motion of the pendulum (Pendel) is instead sensed by means of a 3-plate (differential) capacitor, where the two outer capacitor plates (Kondensatorplatten) are fixed, and the pendulum mass is the moving third plate. The fixed plates appear to be made of brass, while the pendulum is aluminum.
Joe Gwinn