Is there a Drupal module that implements a (+/-) button with a counter textbox at the side?
There is already a module that gives you a vote up/down button, just like the one we have here on SE: https://drupal.org/project/vote_up_down.


  Allows votes on some drupal entities and provides the base for implementing votes on other entities.


It is still under dev for Drupal 7, but IMHO quite usable.  If you find any problems, it will probably be less work to help the developers fix those, compared to reinventing the wheel.