There is a app for iphone or Android called liveBPM.   A lot of bands use it.    I usually
have if going when we play.    Very useful tool.    We also use it in rehearsal to
identify dips or spikes in the tempo over the course of a set.
We generally try to play between 110 and 120 depending on the set and how it matches up to
the dance.     Higher for squares, around 128.
As a caller I will sometimes ask for a tempo range that works well wih a particular dance.
  
Most of you are probably familiar with liveBPM.   It’s been around a while.
Rich