Taking voice input from raspberry pi and sending converted text to arduino to turn on relays
Probably the easiest way would be to set up a serial link between them, although there are many ways it could be done; This link looks helpful, as both boards have serial capability, or USB with Pi as host &amp; Arduino as slave should work perfectly well (but a more expensive bit of wire).

An alternative might be an Arduberry?

On the Pi side, there is a sort of meta-answer here - obviously, the Raspberry Pi stackexchange would be the better forum to look at that half of the project.