Pauly
Tower sells them I see 2 in the Catalog right now. One is called the Tower hobbies Digital LCD mini Tach $21.99 the other is called the GloBee IntelliTach LCD Digital Tach @ 27.99. This was in the Tower Talk that you get about every other month.They work on the light strobing through your prop. You test there accuracy with a florescent tube light fixture. I think the figure was 2500 RPM on a 2 blade prop for the light test and 3600 for the three blade prop test, I think for initial set up are pretty good but I don't use them much after. Like I said I do not fool around with the setting after. I need them because I am hard of hearing and have trouble hearing the engine sound as they change.

The DiBo