I found this jump rope with a counter.  It has a counter attached to  one of its handles and can increment from 000 to 999.  Isn't that cool ?  Now you would know how many repetitions you made.  

Cool ! ... Until I found out that the counter is manual.  It displays the number of repetitions alright but you have to press the button each time for it to register.

I don't think I'd be able to push the counter to increment when I'm tired.