Hey bl4d3,
thanks for your reply!
Because i work in electronics, i can´t really say, which way is secure. I´ve learned programming by myself with the work with arduino. But I found something with QR-Codes we can check for this:
Another question:
Do you want to add more different Sensor an actors the people want to use, or do you thing it is possible to add a kind of "open format". I mean a "device" which shows values from the arduino. Then the users can program their own code with many sensors - or what ever they use - and in your Android-App you can define a field from type int etc...