Since I aquired an Losmandy G11 mount without any goto provision I decided to create my own solution. I was a bit reluctant to use a Gemini, mainly because of the cost, but also due to the reliability since the servo motors are somewhat prone to failure. I also like to have complete control over the software/firmware so that no "show stopper" issues will ever be a problem for me. Looking around the 'net I saw other goto systems that seemed capable, but either they had needlessly complex hardware or were commercial systems that cost about twice what they should.
OnStep is a computerized goto system for stepper motor equipped mounts. It was designed, from the beginning, as a more or less general purpose system and provisions were made in the firmware to allow for use on a variety of mounts including Equatorial (GEM, Fork, etc.) and Alt/Az (Dobsonian, etc.) It uses an LX200 like computer command set with a few extensions to suit hand-controllerless operation.
In addition to the wide range of software supported through it's ASCOM driver, many software packages work directly with it's LX200 protocol. These include Cartes du Ciel, Stellarium, SkySafari, etc.
My hand-controller App for Android devices is available in the Google Play Store. It allows you to Un-park or Align the mount to get going, then startup SkySafari (for example) and connect (using Bluetooth or IP) to have a full planetarium type control application... All from a cell-phone or tablet.
Please visit my StellarJourney.com site for updates, links to OnStep resources, my other astronomy software, or to see some Images taken with the assistance of my OnStep operated mounts.