Looking for practical Arduino projects? This guide shows how to control a relay from your smartphone using an Arduino Uno — ...

Microduino actually isn't the smallest Arduino clone on the market. The Femtoduino, boasting the "same power and pin count of an Arduino Uno," measures just 0.81" × 0.6".

There’s a small phone application to drive the Bluetooth using App Inventor. This would be a pretty straightforward first project and — of course — could be useful for any kind of animal.

Today, Coin announced that it will offer up an Arduino Bluetooth Low Energy module that’s designed to be small and easy to integrate into hardware hacks and products of all kinds.

The watch is built around an Arduino Pro Mini, a scavenged Nokia LCD, and a BlueSMiRF Gold. The Bluetooth connects to a Nokia N900 with a little Bluetooth client app [Ahmet] wrote.

Compatible with the Arduino Uno the new Bluetooth board allows you to remove the need for a USB cable connection making your development and applications more flexible.

I'm a big fan of the Teensy, which is both a lot smaller than standard Arduino and (in the current version) a lot more powerful and easy to program. Not quite this small. But it retains USB ...