Sorry for the slow response @Came2meca
I have seen that device and considered it as well, however I had a bunch of arduinos laying around as I like to build a bunch of projects so for me I wanted to work with something I already knew. But Here are my major lessons learned and advice on doing something like this:
1. Go with the arduino and use either bluetooth or wifi to talk to it via the android. I have it hard wired and it is kinda a pain (as I currently havent completed the android side of it cause I have 3 other android projects Im working on that are more important). For bluetooth here is a good starting Tutorial
2. Make the system work with or without the android. This was important to allow it to still work even though I havent finished the android. Plus most the time it is easy to change the temp or pump manually. Also I didnt want it to be fully automatic as I enjoy the brewing process and wanted to be involved, just wanted to have better control for more repeat-ability.
3. For the Android side of things there are some app buildings for basic apps if you want to just control everything. For things more complex like reading recipes and control it from there is going to be a big undertaking. I have an app made to read recipes already and its still a big task to make it function off of that (which is my ultimate goal with mine). I would start basic with simple control of the elements and pumps and as you learn more increase the features. Also for learning, google is your friend, tons of tutorials/examples for every aspect of android and stackoverflow.com
is a wonderful community to get specific questions answered, when I was learning (and still now) I used it constantly. They handle all types of programming as well not just android
My biggest advice to anyone tackling any kind of project like this that involves programming is to get a good design and flow chart of what they want it to do. I use excel to create diagrams and maps of what I want it to do and get a giant overview picture figured out first before I even start programming. It helps you to stay focused and know what you need to do.