Vibration activated hour meter. Anyone use these?

[pigpenracing]

My J-3 was rebuilt back to all original and does not have a hour meter or tach time. I have been using a stopwatch and writing down each flight. I would like a hour meter to keep um with oil changes etc. I saw this little unit and wondering if its good or junk? Seems simple since I don't have electrical in the plane. The other option is the style you wrap around a plug wire. Looking for a simple option.
http://www.aircraftspruce.com/catalog/inpages/t56c1.php

 

[cashflyer]

 

[dimcuesta]

 

[EAABipe40FF]

 

[dimcuesta]

 

[EAABipe40FF]

 

[pigpenracing]

 

[EAABipe40FF]

 

[wanttaja]

 

[HighTow]