Developer Daniel Lu from RasVector Technology in Taiwan has released a demo app for Android built in Delphi Firemonkey that allows you to control an Arduino. There is a video where he demos the app and he shows it changing the color of an LED on the Arduino when he selected the color in the Delphi Android app. There are actually two different demos. One connects to the Arduino via Wifi and the other connects via Bluetooth. Source code for the Delphi app is not provided as far as I can see but source code for the Arduino side of the app IS provided so that is pretty awesome. The two demos are provided as APK files. In each of the two demos that is a full PDF file (you’ll need your translator) outlining the Arduino setup including what Arduino boards he used, what sites he referenced to figure it all out, and the source code for the Arduino side. Controlling an LED color is a very visual sensor but Arduino’s have all kinds of sensors available for them like air quality sensors, sound sensors, magnetic sensors, etc. You can also connect to Arduino devices from Delphi through a simple COM port serial connection. You can also build similar functionality in Appmethod.