Hi and welcome to the forum.
This is also something I want, most useful if replacing a hairspring or timing a pocket watch. The one thing I would say is I have found a clock does settle down after servicing, you can adjust the pendulum to run perfectly once the clock has been cleaned and lubed but it seems to have a running in period. I have noticed on a few clocks now that I can get the timekeeping almost spot on when it first starts running after a service but after a couple of weeks it might need adjusting again. Just something to bear in mind, this device certainly makes it faster but dont think once you have used it, it will keep good time from then on, it might need adjustment again after a couple of weeks.
I will be interested also to hear which is the best.
Paul 
