Servo Controller
You obviously need a laptop, desktop or mini computer if you are going all out.
In order to make the software work you will need a servo controller. The ones currently available that work with the software are underneath. Personally i would recommend going for the Maestro, it is cheaper and more developed. Additionally the sofware is being developed further with this controller in mind although other controllers will also become available over time.
1. Pololu usb-to-serial servo controller
the Maestro
(click the picture for product page)
the usb-16
(click the picture for product page)
In my personal opinion this is the best one to use as it has several settings and has a high degree of accuracy due to the amount of steps it can send to the servo.
Obviously usb functionality is easier than anything else as you can easily attach it to a mini-computer or a network.
It comes with the possibility of attaching more than the needed 3 servos, so if you want to move a whole bank of sentries or add functionalities that is also possible since this project only uses 3. In order to make this thing work obviously you need drivers to do so. So download them from the site, read the manual you’ll find it in there.