There's been quite a few different Arduino robots made and released based on Arduino, but non seem to have the charm of Ringo. This little robot is small, cute, and features the components you want to have a fun little robot. The palm-sized robot is based on the Arduino UNO, allowing anyone familiar with Arduino to re-program Ringo. The pager motors allow it to zip along the surface pretty quickly, and turn sharply, giving it that bug-like appearance. This is a nice little touch, as a lot of Arduino robots move slower (probably due to being bigger).
Ringo has a few different sensors you can read data from. The 3-axis accelerometer and 3-axis gyroscope allow it to know where it's facing, where it's been and if it's been moved. It can use these sensors to not only track where it has moved by itself, but also if it's been moved by a person (or cat) and respond appropriately. It also has 360 degree light sensors, allowing it to track light from any angle, and a line sensor, so it can track lines and table edges.
It also has a few feedback components too. It features 6 RGB LEDs, 2 on the bottom, 2 on the top, and 2 for eyes. You can create any colour from these, and give it different 'moods' depending on what state it is in. A piezo element allows it to emit sound. It can emit all manner of chirps, buzzes, pings, and whoops, just like a real bug. You can also use it to play musical notes. A USB port allows you to charge Ringo with a standard phone charger, and a separate programming board attaches to allow you to upload new sketches.
Ringo features an IR receiver, and 3 emitters placed at 120 degree angles around its body. This allows you to send it commands from the included IR remote, and program it to receive from any standard TV remote. You can also use them to send command too, so you can have Ringo change TV channels for you! The most interesting part, however, is the ability to have a swarm of Ringo robots. They can communicate to each other, allowing them to create complex, intelligent swarms, and play games with each other. You could even create a swarm to gang up on your cat!
Ringo looks like an amazing little robot - simple, small and cleverly designed, with just the right amount of sensors and feedback to not limit it, but not overwhelm a beginner to robotics. Ringo is out on Kickstarter now, so you can pledge and get Ringo for $89.