Nokia Internet tablets are volume produced, low power consumption devices that are designed to be enough rugged that they can last as mobile devices. Even they are designed to be used as Internet communication devices, thay are also excellent for controlling embedded devices.

This is my presentation in Fosdem 2008,Brussels  about Controlling embedded devices aith maemo Internet Tablet Fosdem_maemo_2008.pdf

Internet tablets have many advantages like price, rugged design and small power consumption compared to both PC-based or special embedded hardware based designs. They have also new challanges because they does not have so wide selection of interface options. 

Some examples of embedded controll projects using Internet tablet is Small aircraft Glass cockpit, Home Automation, Accelleration sensor interface, maemo puppy robot or Carman car data terminal. 

In N800/N810 you have basically three interface options Wlan, Bluetooth and USB. All of these optios require with some rare exeptions separate embedded processor or microcontroller to controll I/O box.

Wlan is fast and versatile but requires in practice multichip embedded controller running Linux.  Good example  is to (mis)use  Wlan routers with  Openwrt

In small series Bluettoth and microcontroller module may be more costly than wlan router.  

The USB is most practical way to expand tablet I/O capabilities. Microcontrollers with USB-device interface price start from some tens of cents to few Euros. USB-device needs something around hundred lines of the code in the microcontroller.

Two easiest ways to connect USB microcontroller to Internet tablet is to use libusb or make device emulationg USB serial converter. In N8xx musb driver has certain limitations that may need some workarounds.