This post will be very short, but it is worth mentioning, nonetheless.
What hardware do I need to get started?
You have made the decision to move towards mobile test automation. Great! Now comes the first major step...Hardware. Obviously, there are only two main options when it comes to development hardware, and the scope of your project will end up making the decision for you.
The Calabash framework can be installed and run on both Windows and OS X machines. However, running a Windows machine will only allow you to test Android applications. So if you are only writing test automation for Android apps, then the choice is yours. But since most apps nowadays are written for both Android and iOS, most of us won't be so lucky.
If you are wanting to write cross-platform automation, the only option you have is to go out and buy a Mac. I grew up on a PC, so when I got started, I wasn't overly ecstatic about making the switch, but I will say it has grown on me. You don't need a $3k MacBook Pro to get the job done, although they are pretty nice if you can get your employer to buy one for you. Any Mac that can run OS X will do, even the relatively "cheap" Mac mini's.
Is that all?
From a development machine standpoint, that's all you need. We will discuss devices next week to wrap up all the necessary hardware.