Brian Cross who works over at the Windows Mobile Division has created a robot named WiMo (Windows Mobile). WiMo a robot that is powered by Windows Mobile SDK and can be controlled through bluetooth. It was written in c# with a small amount of native code for DirectShow so everything is pretty much .Net Compact Framework. Brian also shows you how to build a WiMo out of random parts (he does list them) or a Lego NXT. He says the cost for a WiMo is about $250 without the smartphone. On ebay I found some smart phones for $10 so lets just round that up to $300 if you don't already have one.