A friend and I are setting up our own development board company. So far we have a board that enables Ethernet control of relays and 3 channels of PWM for RGB lighting called SplashBase. I've also written PC, iOS and Android applications so people can control there board over the network. While designing the SplashBase we wanted to make it expandable to allow user to plug in different add ons. This also breaks out all of the IO for people who want to write there own code for it.
So far we have add ons (SolderBridges) that control servos, expand IO, provide more analogue inputs, 9 degrees of freedom IMU and many more. The SolderBridges can be used standalone, connected to the PC or on our SplashBase. We use SPI to control the ARM Cortex M0 processor on each SolderBridge and we 5 chip select lines. So you could stack 5 of these up and control 120 servos, if you managed the power requirements!.
Check out our blog here here : http://www.soldersplash.co.uk/
The SplashBase is on KickStarter at the moment as well here : http://kck.st/SsWOrH
Let me know what you think! any ideas on things we can offer?