I've played with this before. I used Audacity to create an mp3 file with some simple beep tones so I could play it on my phone and experimented with various tempos. You can even use different sounds to distinguish between the various parts of the swing. It's definitely a good way to groove a very specific tempo.

As for the actual tempos, a Google search on the subject should pull up plenty of articles and discussion boards with various suggestions to try. Zepp Golf also has a recommended tempo. I think it was like 3:1 for a full swing? I could be wrong. I borrowed one from a friend to try out, but never fell in love with it and forget what exactly it was.

I the same number of beats as the number of heartbeats I have a minute which is around 70bpm. I used this with my putting and I think it's helped me a lot.

Jack

I use one for putting. I have a cheap korg and plug in earphones when practicing. I set it at 70 bpm, and in 4 beats:

1. Look target
2. look at ball
3. take a back swing
4. hit the ball

I may take it down to like 50 and try it on a full swing one day