I want to talk about interesting service http://remotexy.com/ with which to easily connect Arduino with Android smartphone over Bluetooth. This service is different from all the others I looked at, the fact that you can have different buttons, switches, joysticks on the screen of the Android smartphone. In the visual editor you choose these controls and place them anywhere on the screen and in any quantity, in accordance with your task. For example, I will cite a few screenshots of possible interfaces.
http://remotexy.com/img/screen1.jpg
http://remotexy.com/img/screen3.jpg
http://remotexy.com/img/screen4.jpg
Yes, you can put on screen indicators that will display the status of your task in Arduino.
How to use it? It is very simple. After you create your interface in the visual editor, you can get the source code for your Arduino. The source code will be finished sketch that you download directly into Arduino or supplement it with your own tasks. Of course do not forget to connect the Bluetooth module to your board. And that’s all. On the download page of RemoteXY service you must download a special application in your Android and can connect with your Arduino and manage them.
For example, you can watch this video