I have just completed a small project to add encoders to my 12" Dob and connect it up using Bluetooth to the SkySafari app running on phone or tablet. I am amazed how good this setup is. I managed to move effortlessly from one object to another and have never viewed so many objects in one hour.
I used an Arduino nano with bluetooth adapter and a couple of cheap encoders from China (£9 each off Ebay) all hooked up with patch wires, so no need to solder. It fits neatly into a small plastic box and is powered from a small phone battery pack. The whole build only cost about £50 and has transformed my viewing. I no longer have to spend ages trying to star hop in light polluted skies where half the stars cannot be seen.
The encodes were the key as other options I looked at used expensive 4000 PPR or 10000 PPR encoders but for visual observing using a Dob I felt this was over kill. I opted for optical encoders with 600 PPR which, using software to detect each rise and fall on both channels, gives 2400 PPR which is enough for visual.