Together with a Connect-PI Web application that allows you to access your Arduino boards from your desktop computer, laptop or smartphone using a web browser.

Here’s a tutorial if you get stuck. You’ll also need an Arduino-compatible microcontroller and an appropriate way to connect it to your computer (an A-to-B USB cable, micro USB, or FTDI breakout).

The pcDuino3 nano is now available for $39. This tiny computer features an Allwinner A20 dual-core ARM Cortex-A7 processor with support for Android and Linux.