The BrickPi is an Arduino-based add-on board that works with a Raspberry Pi to allow you to control many of the LEGO Mindstorms components. Mindstorms is compatible with LEGO Technic so you can build cool robots by adding construction pieces from sets you may already have.
The BrickPi can be programmed using the Python language so the complexity is hidden. Python is a popular choice on the Raspberry Pi once kids are ready to move on from the graphical Scratch environment. There will be Python libraries for controlling your LEGO robot using the Brick Pi / Raspberry Pi combination. They also have plans to support programming from Scratch which would be cool.
This is an interesting option for older kids who are already familiar with the Raspberry Pi and may already have LEGO Mindstorms NXT components available. The ability to use multiple motors and sensor means you can build some interesting robots that can pick things up, make decisions based on inputs and do a lot more that just drive around.
The pairing of two technologies that kids are likely to be familiar with or want to learn about is a great idea. And the Python programming language is a good one to learn.
There are some example programs available but it doesn't look like there will be a lot of educational material initially so early users may need to be willing to work some things out for themselves. But the BrickPi is clearly intended for educational use and the team want to develop more resources.
BrickPi has an open design so you can built your own if you have the skills and time. Or you can pledge and choose from various options depending on how much work you want to do yourself and whether you want a Raspberry Pi and/or a case for your BrickPi.
The case mounts a BrickPi and a Raspberry Pi and has connection points for LEGO Mindstorms / Technic pieces. The whole systems is powered by a 9V battery including the motors and sensors.
We've seen quite a few programmable robot kits recently and they all offer something a bit different. Sparki is Arduino based. My kids are younger so we're planning to get a LEGO Mindstorms EV3 kit when that comes out later this year, I think they'll benefit from having a kit that comes complete with models to build and educational material.
But for older kids and anyone who wants to have fun building robots with LEGO and Raspberry Pi, the BrickPi looks like an interesting option. And if the Scratch programming capability gets developed then I could see a BrickPi being a next step for us if it is compatible with the new EV3 components.