From iRobot ($199 US):

Create 2 is a mobile robot platform built from remanufactured Roomba robots and designed for use by educators, developers and high-school and college-age students. Program or build your own projects or start with our sample projects provided online. Create 2 is ready to go, right out of the box, so there is no need to assemble the drive system or worry about low-level code. Other Create 2 features include:

• Serial cable sends commands from a computer or other microcontroller to the robot
• Preprogrammed behaviors can be controlled via Open Interface Commands
• Built-in sensors allow the robot to react to its environment
• Drill template on faceplate shows safe drilling areas. Removing the faceplate exposes the serial port.
• Robot returns to Home Base to dock and recharge. Rechargeable battery charges in three hours.
• Compatible with Roomba 600 Series accessories including batteries, Home Base®, remote control and Virtual Wall®

What are some of the things I can do with iRobot Create 2?

Program movements, sounds and the LED display, as well as read all of the robot's onboard sensors
Add an external computer or microcontroller with additional sensors and actuators to transform Create into exactly the robot you want. Add a camera to build your own camera bot! Use our 3D printable file to create a storage bin and ensure your additional electronics are safely housed within the robot's chassis... (details)