I don't know for sure how this would be made, but I am guessing that an accerlometer could be modified to do this. Though, these might be too costly to justify owning, I imagine renting them from the hardware store.
The Wobbleometer can be fastened to the center of the ceiling fan. The fan is turned
on, reaches top speed and the Wobbleometer indicates a number - say 35.
You are now ready to begin balancing the blades. You put the balancing weight on one of the blades, turn on the fan, wait & a number on the Wobbleometer shows 39. Hmm, not that blade. You move around to the other 4 blades and get 17, 25, 28, and 14.
Aha! so it's the last one! (it's always the last one.) Now you can move the balancing weight around on the blade. At the tip, you get 10, at the base you get 19. Hmm. You put the balancing weight 3/4 of the blade length out & you get a 4. No perceptible wobble really.
This was so much easier than eyeballing it like I did on the last one. Towards the end, I was wondering if I were wobbling.