Having bought the GloBee before I went with the TNC tach, I think I can comment on the differences between the two which I observed.

For the price I guess it's an okay tach but it doesn't have the range of the TNC, it's more intolerant of the lighting conditions and prop type i.e. wood vs. carbon fiber, RPM reporting has much more fluctuation, and it tended to read higher RPMS on a given engine/prop combo than the TNC.

This particular item, a tach, really is a case of getting what you pay for...