We thought that connecting an Arduino to a Raspberry Pi was overkill ... [Jan] uses the PHP serial class to communicate between the RPi and Arduino (dead link; Internet Archive).

and even serve as a serial monitor where you can print messages. If you're more interested in programming with C/C++, there's an 88-page guide you can refer to. The Arduino Nano and Raspberry Pi ...

A Raspberry Pi with a camera is nothing new ... You can connect via USB, serial, SPI, or I2C. Internally, the camera processes at 60 frames per second and it can remember seven signatures internally.