Wow, it's crazy how this post exists, I was just thinking about how an automatic titration device could be made using Arduino.
Anyway I don't know if you've had any luck using the servo, but there is an alternative method (though possibly less accurate).
I pretty much stole the idea from vernier, but you might try using an infrared sensor as a dropper counter. So basically mix this idea:
with this sensor,
and so for each drop a pH reading is recorded thereby creating a titration curve. From there you construct a second derivative graph to receive the equivalence point.
The downside ... is that the drops will each be the same amount and so there is no adjustment for what might be a huge spike in pH.